There are lots of different software options that allow individual payments however, so one person doesn't have to collect the money from everyone. 

So I purchased 4 quads but they are zoned commercial instead of residential so I’m having a little tough time wondering if I should do them individually or all together on a commercial loan.

Flexibility -Hard money lenders are sometimes individuals or private lenders, which means they have more flexibility over terms and interest rates.

What would I need to propose to a new individual to bring into the deal as a guarantor during a refinance?

Set up times to meet with each one individually and lay out your expectations and sign your lease if you can't get one from the owner.

It sounds like I need to do more research into individual lenders and see which one I connect with best and would be the most responsive.

Just get rid of him and find a qualified renter to replace him.When more than one renter occupies, they are under "joint and several liability" which means each individual is 100% responsible for the terms of the lease.

And all the lenders that said they could do the loans individually for each house, then said they couldn't do it because they're residential properties in an LLCs name.

I mention #2 because most hard money lenders will require you to take title as an entity and not an individual.

Advantages: you can scale, the building qualifies for the loan, numbers work better, the building is treated as a business and valued by the NOI instead of being valued by the comparable in the area.Disadvantages/Things you need to be aware of:  If you have never done a commercial deal before usually a little harder to get financing so I would talk with a loan broker instead of going to individual banks.