I have just one criteria that I look for - profit.
It's all just numbers.
It's a balance of risk vs reward vs ability.
Risk: How old is the property, is it in a HPOZ, are there any legal issues, permit issues, occupancy, can you get out quickly, is there demand, what happens if timelines extend, can you afford it...
Reward: Is it commensurate with the risk?
Ability: Do you know enough to mitigate the risk? For example is a gut rehab or the buildout of an ADU on your first flip?