I actually offered $174k and rolled my closing cost into the loan.

But depending on when you bought your house and your mortgage rate, it might be possible to convert it into an STR with enough cash flow to more than cover the cost of renting another dwelling as your new primary residence. 

Total cost including acquisition price of $2.35m.I believe we will be able to create a total of 20-30 units in this building. 

Of course, this depends on your unit blends... 3 beds are in HIGH demand.  4 beds are instant refills (and warrant annual rate increases).Hubbell CBRE puts out a rental report every year. 

You can go to the City to confirm but I'd assume the  architect is correct with the timeline and potential costs. 70k for windows and doors sounds like more than enough.

The 70% rule is a common guideline the rule of thumb is to never pay more than 70% of the after-repair value minus repair costs

Using the BRRRR method, you can actively increase the property's value, which is then reflected in a new appraisal when you refinance.

If you're not currently listening to books educating yourself, I'd start today.A few I'd highly recommend...Buy, Rehab, Rent, Refinance, Repeat - The BRRRR Rental Property Investment Strategy Made SimpleFLIP - How to Find, Fix, and Sell Houses for ProfitThe Book on Flipping Houses How to Buy, Rehab, and Resell Residential PropertiesThis book is not currently available on Audible but a must readThe Book on Estimating Rehab Costs - J Scott

Some lenders may require a second appraisal, if the value is over 20% of the initial cost. 

There is a difference between "best" and "lower cost".