There are many different criteria for choosing a camp spot if you are living full time in your rig. Don’t forget the advantages of being old … the senior pass will reduce your National Forest campground costs by half.
If you are on your way to a specific spot and just need a night
Pilot/Love gas stations. Do not take up truck spaces. Good restrooms, great showers, open all night, relatively safe.
Hotel/motel parking lots. Usually very safe if you pick a high end motel.
Cabelas, Walmart, Cracker Barrel, Bass Pro Shops and all night fast food places. This is a bit less sure. Ask first. Many towns have prohibited Walmart from letting people stay over night in their parking lot. Buy from the business, then ask for permission.
If you want to stay for a week or more
freecampsites This is a great web site. Most spots are for a night or three, but some are for longer stays. They rely on us (campers) to report back. Do it!
National Forest dispersed camping. Go to fed site, pick a state, choose a forest, click on recreation, then onto camping. You can pay at a regular campground in the NF, or you can do dispersed camping. For example check out NC Nantahala dispersed camping. Also, go to the field office of the National Forest and as for their MVU map. Motor Vehicle Use Map. If there are dots next to the road on the map you can camp there for 14 days.
USDA Grasslands dispersed camping. Many grasslands offer dispersed camping. For example check out Cedar River Grasslands in Dakota.
BLM land. Wide open spaces for free camping and some paid campgrounds. Check out their site. This camping is great if you like being outside without many other people.
This is a free site in New Mexico, with tables and a pit toilet. Great hikes, beautiful trees and lots of history.
If you want to stay for an even longer time
The LTVA (Long Term Visitor Area) lets you stay several months for a flat fee that is very inexpensive ($180 for 7 months). Areas are restricted by whether or no you have a “self-contained camping unit. Self-contained units are those with a permanently affixed wastewater holding tank of 10-gallon minimum capacity. Non-self-contained units are allowed only at Mule Mountain, Imperial, and La Posa LTVAs.”.