Lease agreement/Contingent clauses

[Matthew Parent]

Hi.. My wife and I would like to purchase a home.   And I would like to rent out my condo to help pay the mortgage.  Actually, with my low income, the lenders are asking for a signed lease to include with our documentation.   Otherwise I most likely won't quality for a loan.   Any advice on working a lease agreement, where the tenant only moves in if I get approved for the mortgage?    Is it a simple clause?   And if I can't get a mortgage, the tenant doesn't move into my condo.    Thanks for your advice on this.