Mortgage rules for renting out a vacation/second home?

[Max B.]

I'm starting to look for a vacation house, but am getting a bit confused about the restrictions/rules on renting it out. I would like to use it for short-term rentals during times when I'm not staying there.

In the process of getting pre-approval for a second house, I had one lender (Rocket/Quicken) tell me that I wouldn't be allowed to rent it out at all (not even part of the time), and would need to get an investment property loan if I intended to do that. But other sources online seem to indicate that it's OK to rent out a second home as long as you live there yourself at least 10% of the rented out days or 14 days, whichever is higher. 

Can anyone clarify what the actual rules are, or does it differ from lender to lender? And do the same rules apply whether you have a conventional loan or a jumbo loan? I'd ideally like to get a jumbo for some of the houses I'm looking at, but not sure if that would prevent me from renting them out. Thank you!