CopperCyclist
Veteran
In terms of carrying a folding bike in a car... I don't know how big your car is but if it's a small city car, I've found it not as easy as carrying a suitcase. My Brompton won't fit comfortably in the boot of my Nissan Micra (engine size 1.0). My car may be one of the smallest of all city cars but the Brompton has the smallest folded size of its kind. I expected it to fit into my car easily but apparently it won't. It somehow fits behind the driver seat but it's because I'm a very small person and the seat is pushed forward more than the normal person would do. Obviously it can be carried on the back seat easily with any car though - but you might still have to struggle with lifting it up and squeezing it into the back seat if it's a 3 door car.
On this side of things I'll throw up a counterpoint... if you're thinking of a folder just so you can put it in the car for ease of transport for casual riding, you may not need to. I have a Mazda 3, which is a very 'normal' sized hatchback. I can transport either my cyclocross, or my MTB (not both together) easily, without removing any wheels by putting the seats down.
Obviously this means not being able to use the back seats, but if it's only to transport me and the bike to a park this wouldn't be a problem.
So depending on what car you have, you may not need a folder, which leaves the world of cheap bikes from EBay or even Halfords open to you as a starting point to see if you get into it...