I put in my leases that tenants are responsible for cleaning snow off of their vehicles, the porches, and any walkways the town doesn’t plow.

Not something you should DIY with just input from the internet. 

Airbnb won't support a fee to the guest staying longer unless you have it in your listing or rules but if you do, and it was an inconvenience for you or your cleaning team, I would enforce the rules you've created.

Yes they get dusty but don't you have to clean everything when they move out anyway?   

The tenants weren't particularly clean, their rents were about 30% below market, and they had a bunch of cats.

It will become pretty obvious to them when they see you making repairs, cleaning the place up, etc.

If not, you need to be bery careful.....if they get the City involved and you have violated Code, you could be in big trouble.Like @Theresa Harris said, get them out ASAP, clean the place up, make it CODE COMPLIANT get a COO, (Certificate Of Occupancy) and do this right next time.Just my $0.02

If you have a few years of revenue for the EIN, if the books are clean you'll be able to get a mortgage as long as the revenue supports the loan.

@Benjamin SulkaThis one was mostly cosmetic: paint, carpet/floors, light fixtures, trim, landscape clean up, rodent remediation, bathroom vanities in the 1/2 baths, and some of the windows.Rehabbed one unit at the time aside from the windows.

Aligning with a mortgage lender that puts their clients first pays off when the going gets tough..and it always gets tough no matter how 'clean' the borrower.