Here the deal,

So far your idea is awesome. I would most likely dump the leased/rented car for buying a cheapy. Take a mechanioc with you or have him look at it prior to sale finalization. I have purchased many a car under $2500.00 that have odne extremely well.

Plus insurance is cheaper once you own it. You should save money. Use the internet to help you find the car. Next, being scared is a huge thing for everyone, ignore it.If nobody did anything because of fear we would all be screwed. Plus your used to a stationary home.

I would also rethink the leaving point and return point so you may acheive a full circle of the US. it makes it easyier to navigate. You may even be able to set it up so you hit the state that get a nasty winter and hit those prior or after winter. IE take the northern route when you get here from Maine to CT west to Cali then head south as you'll miss most nasty weather the north has to offer. Place you wont travel in the brutel heat of the southern states during the hot months.

Lastly. Start an exercise program of running or walking, push ups crunches. Get so exercise bands for resistance. Retaining some structure in your life may help you enjoy the trip more. And you wont end you with the car seat ass when all is said and done.

If ya need help with any of the things I mentioned just ask. I'd love to help out.