I could pretty easily have a team of rehabbed for the construction.I'm also fortunate to know a couple of really good real estate brokers for the disposition. 

Also a investor should avoid ARM (adjustable rate mortgages) as they could very easily lose their investment when the interest rate spikes up.  

I don't let tenants change HVAC filters because if they are installed backwards, they restrict airflow and can damage a unit.

I stay within a basic protocol of 3 bedroom starter homes that I can easily sell one day when I am ready to move on…  That said, I am looking at a few condos (that were coverted from apartments) for super cheap.  

With the rental income I can easily save over 1000 every month and use that for the next project.

Computer models also benefit from lots of tuning, machine learning, and if the company is good some really expert tweaks to take into account things newer folks would miss.Doing it manually is great because a person can sometimes easily see something that the computer model misses, and can take into account other things - conversations with owners, etc - that the computer model simply can't.Generally I find the computer models do better on cookie cutter deals, and people do better on unusual deals.

Then you have closing costs, realtor fees, carrying costs, utility costs, taxes, insurance . . . . assuming a 6 month close-reno-sell-close, you can tack on another $20K easily. 

Could easily add 3 more trailers on the open lots for another $1500/month for a total income of $5625 and only add another $400/month to the mortgage.Am I missing something??? 

However, I do save a good deal of money from my W2 job and I could easily make early principal payments to get to 75% or 80% LTV.

They could easily appraise for quite a bit more, which could give me roughly 30K per house I can put to other rental properties.