We're also wondering if we put in writing the following and they agreed via email if that's sufficient:#1 they are still financially responsible until we are able to rent the space#2 we're charging a turnover fee $1k to let them out of the lease early and collect that immediately#3 security deposit will be returned according the the RI tenant laws (ie place is left in same condition as move in)#4 room is made available at reasonable hours for showings/open houseOr do we need to hire an attorney to provide a lease addendum stating an early termination fee?

If you get into a 3 or 4 unit, you will have to perform what is called a "Self Sufficiency Test." 

This is mostly due to our homes comfortably sleeping 15-20 people and being able to target multigenerational groups who can split the rent.

Your basic insurance policy with $300,000 in liability coverage should be sufficient in 99.999% of all lawsuits.5.

Do you have sufficient capital reserve should the renovation cost more, take longer, or fail to lease up right away?

By using an extra bedroom or units in a multifamily property to rent, house hacking can turn a home that’s already owned into a property that generates rental income.Here are some common strategies people use when looking for a home to house hack:Multifamily housing where one unit is a primary residence and the remaining units are rented to tenantsSingle-family homes with multiple bedrooms that can be converted into a self-sufficient suite by installing a bathroom and kitchenetteHouses with areas easy to convert to bedrooms, such as homes with a den or playroom that can be turned into an additional bedroomHomes with the basements, attics, or garages already partially remodeled are good candidates for house hackingProperty with a large lot suitable for building an additional dwelling unit (ADU), which is a free standing dwelling similar to a guest home or in-law unitAll the best!

Using 75% LTV as an example: The lender puts up 75%, and they expect you to put up 25% (as well as have sufficient income from the property, income from other sources, cash reserves, and good credit). 

I'm seeking the 80% as I know that will free up the cash desired to undertake my next property + sufficient liquid reserves.  75% may get me there, but not positive. 

I've heard various opinions on opening yourself up to this type of liability ranging from "I never rent a property with a pool/hot tub" to "make sure when screening the tenants you make it a requirement they have sufficient insurance coverage" to "having a hot tub onsite for short term rentals is key."

Generally speaking yes, using a HELOC as a downpayment on a commercial should not be an issue especially since it sounds like you have sufficient income to support the debt payments