My ex has been paying the mortgage on our property in lieu if child support for almost 7 yrs. If we sell the property, how would the equity be divided

It's impossible to say how the equity will be divided unless I know who's been living in the house, and who's been paying not just the mortgage but taxes and upkeep. This is a math problem. Even  if you've been living in the house with the kids and he hasn't, the mortgage payments are not necessarily a substitute for child support. You need to figure out, based on his salary, what he should have been paying you these past 6 years (you can only sue for child support going back 6 years) and what he did pay you, and what if anything else he owes you/ you owe him, and that will tell you if he currently owes you money.  If you don't know his actual salary (and unless you've seen his tax returns, you don't, and if he runs his own business even the tax returns might not telll the whole story) it's unlikely you'll ever find out without taking him to court- which is what you should do. You need to have a child support order in place, for your kids's sake. The child support is for them, so you need to crunch the numbers and figure out if their dad's been paying his fair share, and usually that's impossible without the help of a court, where everyone's forced to turn over tax returns.