If I were you, I would first check to see what this means " . . . a family may use its voucher to purchase a modest home." You must keep a few things in mind when considering a Rent To Own . . . 1) Typically, there is a down payment amount. This payment varies greatly, however, it usually ranges from $3,000 to $5,000; 2) HUD has restrictions and requirements on housing, so this could cause an inconvenience to the Seller; 3) Rent To Own properties are not as readily available as one may think, so it could take some time to find a home, even if HUD approves it.
Have a great weekend :)