These are commonly lent out at somewhat higher interest rates and shorter terms.

A Home Equity Loan is a fixed loan for a shorter period, typically 7-15 years.  

There's a limit to how long most potential buyers would be willing to do the leaseback, so the shorter the better.

I think you were spot on though for investors who have shorter time-frames and are truly looking to build in real estate quickly.  

They used to have shorter fixed terms and much higher limits on maximum rate.

Shorter term leases. 

Additionally, tenants tend to stay for a shorter time period in a multi family vs a single family.That being said, when bought correctly, multi families can be a very efficient way to grow your business.

On the other hand, you don't want awkward bookings that create large gaps shorter than 30 days that you can get booked and lose income on. 

In such a case, the only way to reduce interest paid and "accelerate" the loan is to go in with a shorter term or make higher payments using 0% funds (you pay no interest on it).In this case, if I were guaranteed a 4% interest rate, I'd opt for 15 year amortization so I'd be able to refinance sooner and extract my equity, if that were a key item in my strategy. 

Yes it can rent out for a little more since its furnished and its flexible on a shorter term lease but I highly doubt people are paying double.