You can use a tool like AirDNA to get estimates of property performance in your specific market and with your typical size and configuration of home.

I’d estimate it to fall between $200k and $400k.

So let’s assume with realistic expense estimates over 1st 5 years you average $250 in today equivalent dollars (it will be a challenge at that starting point).The ADUs are typically receiving valuations below $100k, but let’s be generous to show the scope of the people and say it adds $150k of value. 

DIY A first-time DIYer can expect to spend several hours replacing a kitchen faucet.The time it takes depends on your experience and the faucet's complexity.You'll need tools like wrenches, a putty knife, and a small bucket.You'll also need materials like supply lines, silicone caulk, and plumbers tape.You may be tempted to be cheap and estimate only 30 minutes, but you should estimate an hour to be safe.What about the time to go to the property to figure out if a 2-hole or 3-hole faucet is needed, then drive to Home Depot to get it, drive back to install and then head either to the next job or back to the office?

I have all three kinds of parks- LT RV, POH and TOH so can help with repair estimates but so much depends on location and access to reliable repair services. 

The estimated value  now (roughly) is $200K. 

How do you know how much to deduct for these estimated expenses that you may do yourself or you end up tossing and replacing?  

Looking to rent for $175/night min and total estimate is $100k for the build, aiming for 20% CoC.Any pitfalls/advice for this uncharted territory?

To answer your last question, my realtor has contractor contacts I should be able to leverage for rehab budget estimates, as well as family friends with experience in the construction trades.

My estimate is 90% of the time we obtain a tenant in our first open house.