Can a tenants in common agreement include an arrangement that would allow me to buy "shares" of ownership over time?

It isn't easy to find extra money for a down payment, at this point and so it kind of leaves us in an undesireable spot to be in.

What kind of lot/parcel is it sited on?

plumbming  what kind and how old ...is there parking...outside construction is  what...pictures would help us with the price

Kind of strange.  

Kind of what I was thinking.  

If we purchase the house with our own funds what kind of loan would we need to get for the rehab and can someone point me in the right direction about how that type of financing works?

What you have is some kind of a sink hole issue, where the dirt and concrete is not in contact, or the dirt is very loose that when the slab goes down, it has nothing to push back against it and concrete will sag/crack.

What kind of tenants do you have?

Unless there are laws or regulations in Philly I'm unaware of but there are very few CRE who WON'T want or require you to close any kind of pure investment property in an LLC and usually we have a more difficult time finding a lender who allows a borrower to close in an investment property in their personal name- you should have no problem with this.Feel free to PM me to discuss if you like!