A new-ish, well-maintained vehicle with new tires, fresh oil change etc, if it's left dormant & undriven untouched in a residential driveway for 1 year, will it be driveable after 1 yr?

I did this myself, unintentionally of course. I inherited a car but didn't have a driver's license, so the car stayed on the driveway for roughly a year until I got around to getting the license. I did do some minimal maintenance on it - every once in a while I'd go out and start the engine, I moved it slightly back and forth in the driveway to ensure that the wheels weren't always in the same position, and I trickle-charged the battery once or twice when it wouldn't start.

The car seemed to come out of the experience perfectly fine. I needed to change the battery about another year later, after I'd been driving it a while, but I'm sure that's just because the battery was super old to begin with.

Yeah, for the most part. The other commenter is right about that battery, tho. Disconnecting the battery will help, but depending on the type and age of the battery (and temperatures in the storage area) the battery might still not last. Trickle charger might be ideal here, even just a little solar panel for it.

Gas in the tank is another thing. There might be conflicting opinions on how best to handle this, but- I would run the tank as empty as practical, then fill it up completely (so you have all fresh gas) and add a stabilizer. Most stabilizers will keep the gas good for 1-2 years. Best to make sure its an Ethanol stabilizer (like Sta-Bil 360), unless you put pure gas in. Then make sure to drive it a little so the stabilized gas gets into the whole fuel system.

Otherwise, give it a good wash and then a cover for it if you can if it’ll be outside in the elements. Depending on the storage environment, things could still start growing on it, inside and out.

Disconnecting the battery will help avoid the possibility of corrosion seeping into cables. It's probably not a huge risk in the span 12 months, but it's an easy precaution.
okay you mentioned a lot about gas and stabilizers, what about diesel? My vehicle runs on diesel.
- Diesel keeps better that gasoline but there's differences between grades of diesel aswell. I'm a prepper and I contacted a local dealer to ask about how long their diesel keeps and they told me that because their diesel doesn't contain any organic compounds(?) it should be fine for several years but ones that do might start growing algae. I re-fill my canisters once a year.
- Diesel typically has a longer shelf life, so thats one benefit. A year, under optimal conditions. I believe you can still buy stabilizers meant specifically for diesel.
- There's an algae that grows in diesel. Whatever additive you get make sure it's got a biocide in it.
- https://www.sta-bil.com.au/products/sta-bil-diesel-formula
- Ha, as i was typing that i considered the possibility your car might be a diesel, but decided otherwise….go figure! But ya, as the others have said, there is also diesel stabilizers, but diesel does have a longer life span. Putting a stabilizer in wont hurt anything, so personally, id put it in anyways just to be safe….

Only three things I can think of, two of which have been covered already:

Battery, ideally disconnected.
Gas, ideally add a stabilizer.
Tires, tricky, ideally you'd move the vehicle every so often by 20-30 cm to even the load, but worse case your tires are going to wear out quite a bit quicker after a year standing on the same spot.

Since you gave advice on the battery and fuel:

Tyres go bad through the vehicle's weight, so either raise the vehicle enough so they don't touch the ground, or remove wheels and put it on stands.

Once you make sure the car is secure release the handbrake so it's not engaged for a long period to prevent it from fusing.

Clean thoroughly inside and out to make sure dirt doesn't adhere to paint or seats, that no food is left inside the cabin that can go bad and smells that can embed themselves in the seat foam etc.

Cover with a car cover to protect seals, paint, seats from the elements.
- Tyres go bad through the vehicle’s weight, so either raise the vehicle enough so they don’t touch the ground, or remove wheels and put it on stands.
  
  So what you're saying is that having the car up on blocks, in my front lawn, is a good idea.
- I suspect OP is asking about a vehicle where it’s not known in advance that this one year hiatus will happen, ie there’s a vehicle that’s already been sitting there a year.

One thing no one has mentioned is the brakes. Do not apply the parking brake because it can actually become fused on after a long period of time. The best thing to do is actually remove the wheels and use jack stands. If you don't do that then use chocks.

Before driving it you will want to bleed the brake lines to remove any air that might have gotten in there, and ensure the brake fluid reservoir is full.

The brake lines are hermetically sealed, there's no way for air to get in.

The biggest problem is rust on the brake discs; they will still work but often need replacing due to rust pitting

Full tank of gas, disconnect the battery, no problem.

Why a full tank of gas?
- A partially filled tank breathes air when the temperature changes outside, and every time it does, a bit of water condenses inside.
- guess so it doesn't collect water or rust?

Gas is likely bad. There are other factors that could influence the situation. Is this a hypothetical, or do you have more details?

hypothetical. I live alone and have no one to help with such things, and kinda wanna spend a year in the hospital
- Disconnect the battery. Don't leave gas in it. Make sure you've got proper antifreeze mixture in the coolant, if you're in an area where winters get freezing. And if you can, get a proper car cover.
- You OK bud?

Many things and factors to consider. Rodents may chew the wires off, electronics may corrode, plus, everything others cited. All in all, I have stored a vehicle for almost two years without any precautions and drove it without any problems.

I'm surprised you didn't face issues like dead battery or damaged tires.

Biggest thing to know is what sort of climate are we talking about? Extreme heat and cold are big factors. As well as sitting the thing down beneath some big trees or in a very dusty place.

I'd make sure it's driven every couple of months or so.

With a moderate climate the gas and tyres are probably fine for a year. And the battery is probably fine if it's left disconnected and charged up again before putting it back in service. But a year is about the limit, after that the chance of the gas going bad, the tyres getting out of round and rubbers drying out is high.

In a more harsh climate, things can go bad much sooner. Probably better to sell it and buy another one, once you need it again. If for example you are going away for a year or more.

Heat/dust isn't an issue (minus maybe cracking the dash of there isn't a sun shield), it's why all the plane and car grave yards are in the desert. Cold/moisture will kill anything quickly.
- Heat is a huge issue for things like rubbers and tyres. In the grave yard they don't care about the things going to waste.

Your battery will likely need a jump start/charge. I don't know enough about cars to say anything else

Or a replacement. Modern gel batteries don't take too well to deep discharge, and modern cars tend to use power even when turned off (listening for remote unlock signals, alarms, cameras, etc)
Thank you

I'd drain the tank and put a cover over it.

I can't say for certain that it would work or not, but that is what I would do

You’re going to get critters inside if left in a driveway.

I would store it somewhere that is kept rodent-free annd climate -controlled. Also, check with your insurance as you could drop collision since you won’t be driving it.

If you have a military base near by you’ll find storage options. Also look for rv storage facilities as they probably store normal vehicles too.

If you store it outside and put a car cover on it you’ll come back to lots of small scratches in the paint and rodents.

A bar of Irish spring in the engine bay will take care of most of the rodents, just don't forget to remove it before driving.

EDIT: Make sure to jack up the car to remove the weight from the tires, and disconnect the battery.
- That soap trick will not work.

I know it isnt the question you asked but the easiest way around this is to find someone you trust who can just use it sparingly, preferably someone with a garage who can keep it out of the weather for you.

It might make a big difference where this residential driveway is. A Los Angeles driveway that's got a shade tree by its southern side, you'd probably not want to cover the car. (And you'd want to be extra aware that our air eats rubber.) In places that get much hotter and/or colder and get more rain/hail/snow/leaves falling on it, the benefit of a cover outweighs its potential to attract rodents.

Gas might go bad and battery may lose charge but other than that it should be fine. Ideally you should start it atleast once a week and let the engine reach normal operating temperature, but nothing catastrophical is going to happen even if you don't. Just more engine wear because of the lack of lubrication.

You'll probably need to at least charge the battery.