Also, does the preexisting relationship hinder investing in such a note once it is sold?

Since most syndications are 506-B deals, you are required to have a preexisting relationship with at least one of the general partners before investing.

If you do not wish to purchase all/some of these homes for a quick flip or long-term holdings then perhaps you wish to wholesale or bird-dog some of these leads to active MH investors in the area.I do know of some folks in the central Florida area that are actively investing in mobile homes inside pre-existing communities and attached to private land.

We have a program that allows owners to legalize pre existing inlaw units, which is what I did, as they waive most city fees, and are generally more lenient with planning and bldg requirements than adding ADU’s.

If you form an entity (LLC or whatever), when you apply for a loan they will look at the owner of that entity's finances, as well as any pre-existing finances of that company.  

Banks only recycle preexisting buildings so often when testing the market. 

You state there were three multi-family properties that were 1/4 vacant when purchased, and you have evicted another 1/4 of the pre-existing tenants over a two year period, in a low income area.

In my mind, pre-existing rentals are easy to understand and reliably get the contributions to DTI.You both have better credentials than I in this field, so I will bow to you :)

One says that all investors must be syndicated, but there is another that allows for up to 35 unaccredited investors, as long as they are sophisticated (i.e. understand the nature of the investment) and have a pre-existing relationship with the sponsor. 

Developing a fund that permits non-accredited members entails compliance with numerous SEC regulations, including limitations on marketing and communication until a pre-existing relationship is established, usually requiring a minimum of three encounters.