I like your way of thinking, and your avatar......
I like to do things cheap also. I have sleep at rest stops before and had a good night of sleep. I find a nice secluded spot, through out my mattress and un roll the bag. I do sleep in my underware to.

Put your boots/ pants under the mattress or in your bag. I'd hate to wake and find no boots in the morning!

I separate my cash/ CC from my wallet. If I ever get jacked and they want the wallet, there not getting your cash. If I'd do it here in my home State I'll be carring. But usually travel with boot knife. The best alarm clock is sunsine on chrome!

I stayed in 06 at a rest stop in Bettendorf IA when I was Sturgis bound. Rest stop guy told me to do it since its 'not camping'. I woke every hour to eye the bike. Got up the next morning and rode the whole way to Sturgis by 11p that night. They wouldn't let me into camp early so I did the same thing beside the bike outside the fence. Going home was worse. It started to storm on me as I slept on a picnic table. So I pulled the mattress up between the 2 restrooms and got a good night of sleep.
Kit and I did it in 07 also to save some cash. Haven't done it since then since I was better at saving. I did find some new 'spots' this year tho for my future ventures to Sturgis.

I like doing it. Gives me that kinda 'free' high we are always looking for.
Another thing is use those coupon books at the rest areas. Sometimes those little mom and pop hotels are cheap and clean. You can always try and split a room with a stranger on the ride.
Depending on your occupation you could always find a fire station and ask if you can sleep in the yard. I know there have been a few of us, FF/medic, that have traveled and were allowed to sleep in the station.