Comparables in the area seem to consist of other manufactured homes, "stick-built" homes, and detached homes.

Also, find someone willing to pay you to learn the job and skills they want to perform.  

Not only is RE local, your portfolio performance will vary with types of assets owned, quality of management, and your local market.

That you will be unable to make your payments and they will have the cost of repossessing the unit, having a non-performing asset become a liability, and have all the costs associated with retrieving and divesting of the unit.

Build a network of prequalified buyers / investors,  ( yes, that means credit scores, financials and verified  funds to close)  so you can place the opportunity with multiple buyers who can perform.

With that being said, don't immediately make changes if you don't see results immediately... however if the ROI is consistently low, then you should be figuring out a way to improve the marketing.  

I have started factoring in the expansion of my emergency fund to my performance metric calculations (e.g. cash-on-cash).

If I can consistently get $100/door cashflow, that is a win for me.A few things to consider:- Agree that you need to sure about utilities.  

I have been in my real estate investing career for two and a half years at this point and have accumulated 5 properties consisting of 15 units.

What is a good way to create consistent leads and even get sellers calling you?