If the monthlies have to cover the mortgage repayments you will likely have to make it a group where people have a share.
Otherwise:
1. you will be left high and dry if people leave the group and therefore stop paying a monthly contribution
2. folks are unlikely to want to enter a group where they contribute to paying off a loan but will have nothing to show for it when they leave.
If your aim is to build hours (how many?) you are probably better off buying a share or doing a deal as described in an earlier post.
Most hour builders have no interest in keeping their share after the deed is done and they are ready to move up the ladder.
Alternatively buy something cheap (like a Condor) fly your hours in it and then sell it on. They are cheap to buy and some of them are on a permit so cheap to maintain too, they are nice to fly (certainly nicer handling than the average spam can) and you learn to fly a tailwheel machine at the same time.
Whatever you do, bear in mind that borrowing money to save money is unlikely to pay off at the end of the deal.