I am a rookie investor working on building my portfolio and a structural engineer offering consulting on any structural concerns you have for houses you may buy, or if you want to know out a wall to open up some rooms in your next flip. 

Unfortunately a lot of the decisions that are being made by PM are just not the right ones (costs of repairs, what to repair vs replace etc) so it ends up being me jumping in to manage them.

This would probably help since the next one I build I could immediately put for sale and do a short term rental while it sells.I have many years of construction experience and have also done a fix and flip, in addition to building ground up construction, as well as 10 years of entrepreneurial experience running a paddle board rental company... i have a BS in Physics from Georgia Tech , a PhD in Theoretical Chemistry from UT Austin, and did Postdoctoral research using Computational Engineering where I designed, manufactured, and tested a shock mitigating metamaterial...

Would it devastate me financially to get that $1800 bill for replacing a hot water heater ?

They are not owned by the client who hires the architect/engineer.

Here in Florida, all the roofs replaced and car windshields have driven up pricing also.The only way it does go down is if we get more providers.

We are having our roof replaced due to storm damage, however, when the shingles were removed another storm came through the area and caused a significant amount of water damage inside the house.

Let's say it's a roof, and the roof has been on for 20 years and now needs replaced.

For example, someone told me I can get cabinets replaced by going to Lowes and they will install them cheaper?

Not if you are investing to replace your income.