Renovate to the standards of they type of tenant you want in your units.As for the furnace, it seems to me like you have an opportunity to replace it now: everything is being torn up anyway, you already have a budget for larger expenses.In my mind, why tear up and pay for a big, disruptive project later when you have the space, time and budget now.Just my opinion though.

Is the rehab estimate based on an actual quote from a contractor, if so how much of that budget is for contingencies?  

The rehab budget is under $75k and I would like for this property to be me very first BRRRR project.

It’s a great system provided you buy correct, rehab timely and on budget, find a quality tenant and can refinance quickly.  

But I follow Paula Pant's anti-budget mentality.

@Hector LewisIt’s possible if you are buying right, have experience to show a lender, and there is a rehab budget for value add.

Also the budget you have.

Welcome a great first step towards financial freedom is to really work on your budget and learn more about saving and investing.

I did research and found the steel is the budget friendly door, but comparing prices between steel and fiber glass on Home Depot, fiber glass doesn't seem that much more expensive. 

Or you can rent a truck and take it to the dump yourself.