buying out family members for investment?

Myself and my two sisters inherited our mothers home when she died 4 years ago. They are wanting to sell to not have to deal with the house. I'm toying with the idea of buying them out. The house is in need of some repair but is in a good location to fix up and either sell or rent. I own, well have a mortgage, on my own home and don't have much spare cash for a down payment, which I hear can be quite high for buyiing an investment property. Q: does, or can my already owned 1/3 interest in the home count as an equity downpayment? or at least in some way help? I was hoping to borrow enough to buy them out plus some extra to do some updating and repairs.

Thanks
Sean