Make a spreadsheet and take your total rent and subtract vacancy, mortgage, capital expenditures/Maintenance, Tax, insurance, and property management (You always want to include this just incase down the road you end up using property management).

I will subtract the Rehab estimate, Holding and Closing estimates from the All-in cost basis to come up with a Maximum Purchase Price (MPP).  

Subtract the Rehab Cost ($20K) and you are left with $137,500 to cover your offer/purchase price, Holding and Closing costs.  

The most important thing to look at is the historical operation of the property, then factor in the expense ratios or nearby properties, consider the differed maintenance, age of building, class of building and other operational expenses you may add or subtract to optimize NOI

As long as your income is less than 150k -for example if you make 50k at work and 50 k from rental income 100k gross earnings from the year you could subtract 1/27.5 years of depreciation let’s call it 50k and 30k of interest and tax so your tax able income would be 100k-80k=20k taxable income-how would being a real estate professional help me making under 150k Would appreciate any help or resources you could refer me to

In general, I think working with a knowledgeable real estate agent can add more than subtract for where you are at.

Subtract repairs, then you have your target purchase price.

If you borrow money to buy your home, you can calculate equity by subtracting your loan balance from the value of your home.

Is 0.75 multiply against what is charged for rent for the month or is multiply to the cash flow I get after I subtract all expenses such as insurance, taxes, and paying the existing home mortgage?

Subtract that basis from the $15000 and that will be your profit.