No banks dont offer anything like that. Find yourself and agent that represents you and find a seller that will do owner financing for 3 to 5 years and then refinance with a bank or credit union.
You'd find a lease-option or lease-purchase either on your own or with a real estate agent. The terms of the lease and the option (or purchase) would be negotiated with the seller. You'd then lease for a period of time. (Kevin's advice regarding 3-5 years is excellent. The longer the better. Don't do a deal with a 6 month or 1 year option.) Then, if/when you were prepared to purchase, you'd go out to a mortgage company and get a conventional mortgage.
Investors also offer lease-options and lease-purchases. In that case, you'd make the deal with the investor and then, at a later point when you were ready and able to buy, you'd go and get a conventional mortgage.
Point is: Mortgage companies come into the picture only when you're ready to buy. Before that, you're dealing with the home owner or an investor.
For tips on how to find lease-options, see http://bit.ly/findaleaseoption
Hope that helps.
You are asking the OWNER to carry you for a period of time, usually 2 to 5 years, at which time you will try to find a Mortgage company to complete the sale.
Good luck and may God bless