Thanks for your insights @William Hochstedler
In this case, I was considering this possibility because...
1) Rehab is mostly cosmetic - $10K-$15K
2) My offer would enable me to buy the property w/ $50K+ instant equity (after factoring in rehab)
3) Rental cash flow would be approx. $400/mo. (before maintenance/repairs)
4) The monthly rent would be less than 25% of the couple's current gross income (according to the listing agent)
5) The listing agent believes that the current owner would be receptive to a lease-to-own to buy back the property in 2-3 years. In such an agreement, I envision the current owner/future tenant would pay $2,000 upfront and $200/mo. to be applied to down payment in 2-3 years. These monies would be forfeited if owner could not obtain a mortgage within 3 years.
6) Between the $2,000 upfront lease option fee and a $3,000 rent security deposit, I would have $5,000 to go toward eviction in a worst case scenario.
But these are all moot points if banks are prohibiting this.