How many c-sections?

I will be having my 3rd c-section in August, my first child was breech, the second we planned a VBAC but needed to have a c-section two weeks early, so this one will be scheduled of course. My question is, how many c-sections are considered safe? We were going to have my tubes tied during this c-section but are having second thoughts that maybe we might want one more child several years down the road...is that safe? Obviously I'll talk to my dr about it but I was curious what others have been told :)