It now cash flows beautifully, which I continue to utilize for other my other properties. 

They need to do all their due diligence including understanding the value that will be added by the ADU, the finance options available, the consequences of adding the ADU (rent control, property taxes, rental limitations, etc), etc.Good luck As with all things, it depends on the investor and the equity.If they are able to leverage existing equity to buy it under a HEL or HELOC, then they are adding equity with no out of pocket expenses, and adding immediate and longterm cashflow to existing stock.We like ADU's because there isn't more land being created in our city that is landlocked...but there is more density available to those with large lot under-utilized sfh.In my market, it typically costs $2 to add less than $1 of value on single build ADUs.  

If the property is sub-metered/ if you intend to have the tenants pay utilities make sure to mention that to them. 

Utilize a 1031 Exchange: Under IRS Code Section 1031, you can defer capital gains taxes by reinvesting the proceeds from the sale into a similar “like-kind” property.

Most investor utilize short term hard money debt to scale their flipping operations where the lender will fund 80+% of the purchase price and the rehab budget which can allow investors to work on multiple projects at once.

The other half of the accounting records is coming from online purchases, utility payments, etc etc where they are sending you an email. 

I pay no utilities and these are all one year leases.2) THEIR CREDIT RATINGCollege students almost always pay their rent.

I am putting it up on Facebook, Craigslist, etc. but is there anything else a newbie can utilize that you have found success with?

I spent 2.5 years getting all the utilities to the property.

Trying to manage a $1M Airbnb rental while it sounds good you got $6500 in bookings you still have significant costs to operate it with maintenance repairs, utilities etc.