I feel like a lot of people are getting in too much of a hurry...buying high and financing themselves to the neck...they are ok until one thing goes wrong...and it will....then the whole ship sinks. 

We all as business owners have to also remember the adage of “loose lips sink ships”.

This low liquidity is why most business seek protection of bankruptcy only to re-emerge later still looking healthy because they found a way to convert some of their holdings into cash to improve that liquidity position.Even a positive cash flow from several different sources will not help you if your cash outflow is greater than that inflow.If you have too much equity leveraged so that you can not gain access to it when it is needed then when the next wave comes you will sink.

The purchase price is $190,000 and estimated repair costs are around $30,000 (need to add a toilet and sink in my unit). 

Ground preparation- need a support surface otherwise they will sink into the ground.  

Or building out a basic microwave-hotplate-sink wetbar so that Airbnb guests have a food prep space without having to enter the main house?

Electric and water off and slowly safely start "demolition" (removing sinks and toilets fixtures) running as much noisy equipment as possible.

I'd have to sink at least $10k worth of work in addition to the $18,000 down payment but I'd get the 10k back on the option consideration. 

Use schedule C PVC plumbing and hardpipe all your sinks/faucets. 

If its LR1, LR2, LR3, NC, or any other high density zoning I wouldn't sink any money into them - highest and best use is to tear them down and rebuild in those zones.