I would like to use the SDIRA of outside investors to fund our purchase and rehab of future flip/rental properties as well as possibly take loans from a SDIRA in order to eliminate some credit card debt we foolishly took on using SEAD Capital early last year. 

I believe it would be seen as forgiving the debt, eliminating your ability to collect it. 

You do Not want to put it in an llc....that eliminates conventional 30 year fixed rate financing.

Well, you Won’t get a 30 year mtg with an llc....it eliminates 30 year fixed conventional loans.

That alone is a way of getting a "part-time job" by simply eliminating the child care costs.

This allows you to directly manage transactions via the LLC and eliminates the paperwork, processing delays and per-transaction fees of the custodian.

There can certainly be increased liability, potentially higher operating costs (keep in mind that some private systems can actually be cheaper than municipal systems, especially if bill backs are implemented) and an increased management burden associated with operating private utilities but I feel many investors immediately eliminate MHP investment opportunities from consideration due to the sole fact that they’re running on private utilities.  

Originally we were going to out it back into the principal to pay the house of quickly (like 3-4 years) and eliminate our debt to fund retirement savings faster.

One of which is eliminating the owner occ requirement for 5 years.

They are not something you use and take to investors and say “oh this must work because it fits this rule of thumb”Shouldn't your specific knowledge eliminate the need for the 30/50 rule?