You could do a 203K, and possibly add space to the residential portion of the property to get that percentage down to 25%, but that would probably be cost prohibitive.Personally, I would look at my options and determine where the best return on the money would be.

They promised access to private lenders that lend based on the deal and not someones credit.

A 3-day cancellation notice, informing you of your right to cancel your contract if you signed the agreement in your home, or at a place other than at the contractor's office or business;All warranties on the owner's rights; A statement warning, in ten point bold type or larger, directly above the space provided for the signature, the following: DO NOT SIGN THIS CONTRACT IF THERE ARE ANY BLANK SPACES.Whether any lien or security interest is on the residence as a consequence of the contract.An enumeration of such other matters upon which the owner and contractor may lawfully agree.Any other provisions otherwise required by the applicable laws of the Commonwealth.A clause informing the owner about: any and all necessary construction-related permitsthat the contractor must obtain such permits.that owners who secure their own building permits or deal with unregistered contractors will not be eligible to access the Guaranty Fund.Acceleration of payment: No contract can contain an acceleration clause that would require any part or all of the balance not yet due to be declared due and payable because the contractor deems himself to be insecure.

For septic lot size matters as for a standard gravity septic you need a space for the leach field.

Welcome to BP @Jared Lillard, there is a lot you can learn about here at the open forum and some videos which you can access as pro member. 

 27 are seller owned trailers 1 seller owned campers 2 lots rented 2 empty spaces

I have access to some funds from my 401k, about $3000, and I'm wondering if that's a realistic amount of money to start out with.

We have three locations currently and we rent all three spaces. 

I would also suggest joining your local REAI (real estate investment association) For a very modest membership fee you get access to a wealth of education and networking.Just some suggestions.Good luck

You just have access to cash anytime w/ heloc.