I hate to say it, and I'm sure quite a few that live here and speak Spanish have had the same experience, but I hear working girls talking about several different guys sending money from the States fairly often. And of course, I've heard the stories of guys having the same novia and finally finding out. Funny thing is, when there are multiple novios and they find out about each other, seems one is the 'winner' (loser) and stays with the girl anyway, either ignoring what happened to the point of denial when it happens again (and again and again).
Maybe the answer is a 24/7 security system with cameras, a computer that registers when doors open/close in the house or condo or something similar. Wait...I've already heard that story too and it didn't work out well for anyone.
As for multiple guys getting together to 'share' a 'novia' and pay her bills...can't imagine it could work between jealousy, time-share arrangements, who pays what bills and just the simple fact that if the girl already has at least two guys paying her then why wouldn't she chose to make a little extra on the side when the 'novios' aren't in the country?
Cudos to Doc's post...right on target as usual!