I see the money but can't get my foot in the door. 

Investors pool money to purchase assets within the fund.

Maybe some specialty programs exist for prefab homes or a custom ADU builder might have his own lender partner they could refer you to... but unless you yourself are an experienced home builder with a track record in ground-up construction, you're basically looking at a hard money or a HELOC.

It's not a lot of money, but after awhile, it begs the question: why am I paying for this? 

You will then have a few options with that rent money....you can put it into principal or you can start saving it to purchase yet another property.

I'd like to enter the private/hard money market as an investor with money to lend.

I recently attended a webinar, Master your Rentals: Save Money and Time with effective Self-management.  

As a PM, we deal with people's most heated topics - their money and their homes. 

Perhaps your kids could help you with video editing, marketing, and other things.While you are getting active income, you could potentially look at wholesaling or fix and flip.When you wholesale, you don't need a license and you don't need money.

It's well worth your time and money to hire an attorney on Monday.