A property good for rehab but not for rent?

[Brian Stein]

So I basically have seen two basic formulas on these message boards to determine whether or not a property is a good buy.

For rehabbing: (ARV * 70%) - repairs = Max Purchase Price

For Renting: Rent * 50 = Max Purchase Price

I would like to buy a property to Rehab, but be able to fall back and rent it if I can't find a buyer quickly... while also having positive cash flow after mortgage and operating expenses.

If I put an offer on a property for $25k and the ARV is $50k (if I put in all new flooring, paint, and redo the kitchen and both bathrooms) that leaves me $10k (According to the formula) for repairs which I could likely do if I'm doing it all myself.

BUT...

That would have me with $35k into the property, and I am only confident of being able to rent for $600... Which would make this a loser according to the rent * 50 = Max purchase price. I would have $35k in a house according to the formula I should only pay $30k for.

Does this make this a bad deal?