In the interest of brainstorming, there would have to be a rental time limit.
The security deposit would need to equal the value of the item. If there is push-back here, I say "If you can afford an SBM or aluminess goodie of whatever, you can afford the deposit". To be somewhat militant about it, if you exceed the rental time limit you can keep it and bye bye deposit....or perhaps the deposit burns down over a short period of time (pro-rated grace period).
......Of course renting an item would also include endless help from forum members willing to jump in and help in whatever way they can.....sometimes whether they are asked or not...
For folks with less technical skills, this is a win, win, win, in that it's way cheaper than going to the Ford dealer or other shop, they get the satisfaction of fixing something themselves, and they learn a few things.....one of which is that you can't be lazy returning the rental item.
We could have a sticky with a list of items available, the rental fee, deposit and the owner of the item (for PM'ing the owner to rent).