While I know perfectly well what it's like to be tight on money, I would make sure to do all I can (ask friends/neighbors, etc) instead of getting under a vehicle with just a jack supporting it.
Money might be tight, but say it's your unlucky day, and the jack gives. The $20-$40 you skipped out on just cost you an emergency room visit, or possibly your life.
And I'm not trying to be "Mr. Riding on a High Horse." I'll be the first to admit I've done some shady stuff.

 

i understand what your saying, but like i said, ive never climbed under the truck when it was on a jack, but i have used one to suspend the truck for more than 5 hrs. nothing happened (not saying something couldnt have happened tho..) but also like i said, im a small enough guy to where i dont need the truck on jack stands to get under it. i personally dont need jack stands cuz all i have to do is pull the side i need higher onto the railroad ties the landlords put in the back yard and i have more than enough room to move around and breath.

 

never ever ever go under a vehicle w/o a jack stand.

a 3 ton is nice. but if money is a problem, two 2 tons are more useful than just one jack. for rotating tires, you can jack up front and rear at the same time. or for jacking up the front, put one jack under each side and take er up. much more stable, safer, etc.

a 'good practice' - when you jack up a vehicle and put a stand under it and remove the tires for awhile, you need some place to put the tires - right ? slide them under the vehicle. if it was to drop, the tires are one more piece of insurance to keep it from smashing you.