Rent to own?

My husband and I just started renting a home and we would like to own it eventually but we have a huge amount of debt and we can not get a loan for the house. We can afford the payments but we are not able to get a loan because of our debt to income ration. The landlord has given us the option of rent to owning so he could buy a house but he needs our down payment to use for his down payment on a new house. Wouldnt he need to keep my down payment in the bank so that we could use it once we are able to buy out right and do we have the papers on the house while we are paying him, so that way we can do things to the house. And how long do rent to own contracts usuelly last for, we have a 12 month lease up in Feb. so would it last until then or could we go longer because my husband will have a better job in 2 years and I dont want to miss this oppertunity. Is it an option to add our debt into our home loan or buy and have to waite a while to refinance and then pay off the debt? Thanks