Right now, you have a property with a great equity position, solid cash flow, and cheap debt (interest rate is low). 

And maybe diversify a little, invest half in a low cost S&P500 fund like VOO and the split the rest across 2 or 3 syndications.

If each property costs $200,000 and your only acquisition cost is a 25% down payment, you will need $850,000 (17 × $200,000 × 25%) in savings, an almost impossible amount for most people.

To me at my current knowledge level, this deal only works if taking over the loan - to limit the out of pocket money to acquire the property since the outside reno and new septic would take up the bulk of rehab costs. 

Make sure your rehab is "renter" cost rehab. etc. 

You can usually get a lender to go 85% of cost or 70% of the As Completed Value for such a project.

Why is your mortgage cost so low at only $44k/year?

The previous owner used it occasionally and rented it out to offset some costs.

You'll find that rental property investing isn't scary at all and a great property manager can actually save you more money than they will cost!

Honestly, I think you're estimated expenses are a bit low.