@Nick Romano they all have their own unique qualities but the important thing is to create a “system” that accommodates all aspects of your operations.

Rental properties are definitely unique investments in that you can experience growth through appreciation, equity, cash flow and tax benefits.

I am trying to put together a list of hard money, portfolio, and commercial credit line lenders where I can set up credit lines, personal loans, private mortgages/hard money loans, or good credit cards in the event I suddenly needed a large amount of funds that stretched past my stock and cash reserves. 

You don't want to touch your 401k for a stretch of a deal.

You also have more access to getting questions answered on remote properties or unique situations to get a "Pre-Approval" based on the scenario.

As @Basit Siddiqi mentioned above, MHPs are a unique asset class and have some intrinsic qualities that make them more tax efficient than most real estate, but you will only have access to that tax efficiency if you have a CPA that understands them. 

Looking on advice of how to stretch that 350k as far as possible.

Your free time does not mean really mean anything unless you have some unique way of helping them. 

@Sean Zhang if the other options above are a stretch or too time consuming, considering investing your cash as a passive investor in one or more other deals that are ready to roll. 

A “System” stretches well beyond just a automated process machine.