The after-repair value determines if the property is a good BRRRR or flip.

Financing is important but your realtor will absolutely be the determining factor whether you purchase correctly or not. 

@Polat CaglayanI've never seen a formula but here is a general rule of thumb for multifamily:The class of an apartment refers to the quality of the building, which can be determined by a number of factors, including age, location, and condition: Class A: These are the highest quality apartments, typically built within the last 15 years.

I'm very good at running comps and determining rehab costs.

I would get together with your realtor, have them tour your property and then run comps to see what the value add would be, then simply pencil it out to determine the return. 

Additonally investor buyers use matrix like cash flow to determine value. 

That will largely help to determine the right fit in the landlord market for someone with a portfolio. 

Start by researching different types of properties, such as residential, commercial, or rental investments, to determine which aligns best with your goals.Building a strong network is also crucial.

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!

I just finished The Book On Rental Property Investing by Brandon Turner, and it made me even more excited and determined about getting into this business.