IMHO . . . it depends on how much rust is underneath. If there is too much rust, then I would say no. But . . . if the rust underneath is ok, then I would consider it.
I'm not sure where you're located OP.
But I'm here just outside of Toronto, Ontario, Canada. In the salt-belt! Lots of snow. So lots of salt on the roads in winter. This really eats away at cars.
We bought an old 2000 Nissan Altima back in 2015. It had a lot of rust. But we just needed something cheap. And I told my wife I wasn't very good at looking after cars, so this was the car that was going to force me to learn what to take care of.
And it did. LOL. Paid $1,600 on the car. Spent $3,300 in maintenance and repairs for the 3.25 years we had it.
But, because we paid so little . . . even with all the repairs, it is the cheapest car (per year) that we've ever owned. I don't regret getting it.
And it totally showed me what I need to keep my eyes on. LOL.
It is the rust underneath. If that old 2000 Nissan Altima didn't have so much rust underneath, I would have kept dumping money into it to keep it on the road. It was a brake change that finally got us to pull the plug on it. Because we didn't want to dump >$600 into the car with that much rust underneath. I was thinking the subframe would go soon, so we just donated it and moved on.
But that is why I am fanatical about rust proofing my current cars. (2016 Dodge Grand Caravan and 2011 Nissan Rogue.)
OP. If your car is paid off, then it is only maintenance and repairs that you are paying.
If you think ~$2,000 of repairs could keep you on the road for 2 years, and there is no major rust underneath (ie. your subframe isn't about to fall off.) then I would (personally) highly consider paying those ~$2,000.
If the car lasts 2 years . . . it could be a cheap 2 years. No car payments. Lower insurance. And no need to buy new floor mats, roof racks, hitch, all if applicable. LOL.
The longer you keep your car, as long as the repair costs don't exceed ~$2,000 per year average, I think you come out ahead, because each additional year keeps bringing your overall average yearly cost down.
But this is why I think, at least here in the salt-belt, paying ~$125-180 per year to rust proof the bottom of your car will pay back in spades at the end of the life of your car.
Take care.
TheRogue!
EDIT: Oh, yeah. We have a 2011 Nissan Rogue with about 147,000 KMs on it. So about 91,000 miles. We just got it in Nov, 2018 used. So a recent purchase for us. It had 7 years of rust underneath. But I've had it rust proofed (Corrosion Free). I think if I can keep the rust level at where it is now, I have no problem dumping money into this thing. I told my wife, I want to try to get 7-10 years out of this car. We've almost got 2 so far. So only another 5-8 years to go!
On the outside, that would mean we'd try to keep this thing until it was 17 years old. Well. The car our Rogue replaced was an 18 year old Nissan Altima, so I don't think it is completely impossible! LOL.