The unobstructed water views for both front STR units can be challenging to determine additional value compared to other 3-unit properties without views.

I have heard that it is common practice that private money lenders collect a monthly fee thru various methods, I'm trying to determine what those methods are.   

Your fixed costs could be something like the following: $5k property tax, $2k insurance, $3k utility (including internet and TV), $2k landscaping (mowing, weeding), $2k or $3k maintenance (if you have a pool or hot tub). 

Those are probably the biggest questions someone needs to know to determine the feasibility of your ask.  

I recommend continuing to learn pros and cons of each and determine which paths (I pluralize it as you should diversify even across real estate).

Quote from @Sofia De Santos Tavarez: Hello, my husband and I are looking to do our first rehab in a different city than where we live (we live in Austin and looking to buy in El Paso), and are wondering how one determines and writes a scope of work and determine what material to buy for what.

I'd say start the process of securing your HELOC if you havn't done so and spend time analyzing deals and determining what type of investor you are looking to be. 

Figure out market rents, deduct expenses to determine NOI, deduct cashflow you want, plug remainder into mortgage calc at current interest rate, then add lender's required down payment.That is how much you offer!

You need to learn how to analyze property and determine if they are a good investment.Here's a guide that describes how to analyze a property.https://www.biggerpockets.com/blog/rental-property-cash-flow...

You can determine if the cost segregation study makes sense by speaking with your accountant and many cost segregation professionals offer a free analysis.