This is literally the entire reason these companies exists - to get this stuff right.As for why, I have no idea why there has been an uptick.

The real skill is understanding the variability and risk in each number which is not always numerical or scientific.

We have done it both ways where we fund purchase and they cover rehab but if the individual is less experienced we do not do it that way, we have them put more money into the deal from the start and fund the draws, reason why is we also had a deal where the person said they would do this and never did anything and property sat and loan matured and it was a pain.Just recognize you will still not get 100% financing for the purchase, so you are putting money in up front. 

I have to evict using the landlord tenant route, but I don't know which reason to choose.

That is if purchasing EXISTING performing investment real estate AND have very good clarity of every facet of the transaction ESPECIALLY reasoning for seller selling, AND you have decent market intelligence. 

Search the BP for ADU appraisals to encounter numerous examples.

The reason sellers cannot sell these properties through the traditional market is often due to certain issues, and 98% of the time, these issues are not beneficial to you as a buyer.

I have gone to numerous RE meetups and discussed numerous ADU appraisals and was heavily involved analyzing one (that gave a value of ~$50k for a ~400’ garage conversion 1/1.  

Our city is rapidly expanding, offering numerous job opportunities and a wealth of investment possibilities.

I can find numerous other similar homes for investors.