My $0.02 - take it with a grain of salt. I have a single B&H in a nearby town (Rockwall) that is slightly less expensive than Plano. It just barely cash flows so far (purchased Oct. 16, rented since Dec.) and that is because I manage and do most of the maintenance. I am still actively looking to acquire currently. To your direct questions:
a) Good luck with this - I've given up on trying to change people. If you don't trust them to "pitch in their fair share" I don't know that I would be mixing funds with them.
b) I can't help you much here because I just don't know. Could one of you personally get the note, and then add the others to the deed? One thing that I can remind you - you MUST HAVE RESERVES, and you will also have closing costs as well as pre-paid escrow items. If you figure $7k in closing costs + pre-paids, then keeping another $6k reserves (you must at least at all times have your insurance deductible in cash: North Texas = hail, winds, & tornadoes) then your $40k is really only $27k of down payment. I'm just going to tell you - there aren't a whole lot of $135k turnkey homes in Plano.
c) I may get jumped on here, but I haven't seen a single turnkey house in *nice* neighborhoods in DFW that will cash flow @ 80% LTV with management in place and conservative estimates for vacancy, repairs, & capex. Hell, the few wholesale rental "deals" I have seen over the past year or so don't even do it. Unless you want to move into less premium suburbs, I just don't see major cash flow occurring. If you are purely betting on continued appreciation - that is a different song & dance. Then the question just becomes how deep is your conviction that the market will continue to trend up?