But, I never used them before for civil engineering and architectural work.My question to any experienced investors is please suggest what is the best route to go about this project ?

I would consider selling, i’m not necessarily saying you should, BUT only hold if you have a very strong belief in the appreciation of this property. 

@Thelma Bal Best content on Cost Seg, bar none, is @Michael Plaks' posts on the subject.

@Grant ShipmanIn my experience with these units are very difficult to manage and people at the 30% level also create a new set of problems.

🫣This doesn’t answer your question directly, but the whole concept is very close to the old time “rooming house”.  

Very few people have the ability and the time to work both sides of the transaction.

Quote from @James Wise:I need to dig up a podcast that I listened to about 2 months ago with Tom Ferry, and the person was giving all the states, You are pretty close to that number on 5 days or more.. 95% range, the industry is very off kilter these days with the low activity of 2023 and 2024 that most people licensed just retired, gave up, or thought they were going to do something and never could get a sale due to bad leadership.

Investing in "small towns" is actually a very broad term.

UPPER FLOOR" which wasn't great but it's the best option support had for me.  

You are still going to get the best rate possible with your significant down payment and with good credit I'm assuming.