That being said, they are extremely costly and expensive and generally do not make sense for smaller transactions. 

Only thing I will add is if you rent by the room, you also have to factor in landscaping costs (mowing the grass) and ideally cleaning of common areas (eg weekly cleaning service).  

Find architects or designers, engineers of all types, general contractor, etc. to design the project, and know how to keep the design where it's functional, cost effective, but has appeal.

Again, I envision five families working together to cost share a property. 

When you start looking for multi families, you should look in their areas because they will be the lowest cost property management option.Can you tell me more about your Myrtle beach property, how you found it and how your experience has been with it?

You clearly have little knowledge of how to run a business and the costs associated with it.

Look into the cost of this for both partners and all the necessary schedules that will need to be generated . 

We are in the process of flipping our primary home and have found costly repairs that are needed, and we simply cannot come up with the needed funds to pull us through when we list in September.

I got the owners to agree to pay for a new water heater for the building (about $4000), and $10,000 of seller paid closing costs.

Arguing never works.Get a good attorney that specializes in landlord/tenant law and accept that it will at times cost money to have them deal with things.