You will not recognize the deposits as income until the option to purchase is exercised or the tenant forfeits the deposit under the terms of the lease agreement.
Per the IRS: Lease with option to buy. If the rental agreement gives your tenant the right to buy your rental property, the payments you receive under the agreement are generally rental income. If your tenant exercises the right to buy the property, the payments you receive for the period after the date of sale are considered part of the selling price. source: http://www.irs.gov/publications/p527/ch01.html
