thanks for the replies, but I disagree that this is a standard, longstanding bank practice. Every heloc application has 3 options: primary residence, vacation/2nd home, investment property. Before the existence of airbnb, the distinction between a vacation/2nd home and and investment property was clearcut: a vacation home was used mainly by the owner and if it was occasionaly rented out short term, nobody knew about it and it did not change the property's classification as a vacation home. An investment property was rented out continuously to tenants and never ever used by the owner.
The two responders seem not to believe in this distinction: if you rent out your vacation home for even one night out in ten years of ownership, it suddenly turns into an invement property. This makes no sense. One might respond 'oh, one night in 10 years does not turn it from a vacation to investment property" but this is what the banks seem to be saying. They are saying if you EVER rent out your property it is considered an investment property.
There are in fact government/IRS rules about distinguising a vacation home from an investment property. They are a bit complex and relate to whether the home is in a vacation area, how far it is from the owner's primary home, and whether it is used by the owner for at least two weeks per year. The IRS DOES let you rent out your vacation home and still consider it a vacation home. My point is that the banks are ignoring these government rules when distinguishing between these two types of properties. That is there perogative. But this would see to have significant implications for all airBnB users. They could start considering primary residence's to be investment properties if they are listed on airbnb.