Repair or Replace HVAC with a tight BRRRR budget

[Brandice Walters]

We are purchasing an REO for our first attempt at the BRRR method. It is a major fixer upper and our budget is squeaky tight to make it work. The AC unit is undersized at 2.5 tons for a 1800 sq ft home. It needs to be cleaned and have a blower motor replaced for an estimated $250. We could replace the HVAC for $5000 and upgrade it to a properly sized 4 ton unit. I am not sure how much of a return replacing it will factor in to the appraisal. Is it worth pushing our budget to the max to replace, or will an appraiser just check the box that there is central heat/air?