I was homeless off and on for quite a while about 6-7 years ago. I only spent a few nights in a car and never on the street but I was around people who did. Some problems are
1) the police (they generally will not let you sleep on the street or even in your car unless you're on private property and have the permission of the owner and
2) lack of toilet and bathing facilities.
3) electricity for some things, like charging a mobile phone and refrigeration of food.
4) you're at greater risk of becoming a crime victim if you're alone.

You might want to rent a PO box to get your mail before you sell your house, too. Most post offices require proof of permanent address now before they will rent a PO box to you.

There's a woman around here who has a van (two seater) and she had the back custom fit with cushions and a table.

When I was homeless, I usually ended up going to a day shelter to take a shower. I was glad to have the shower, but being around the people there was not a pleasant experience.

If I was going to be off the grid again, it would be good to have a small piece of land and either a nice tent or a yurt and a vehicle.

I'm curious why you think that being homeless would be better for your PTSD. I have a friend who's a veteran and has PTSD and spent a little while homeless and it was horrible for him. I used to see him during the daytime and he would look like hell.