Comps adjustment help

[Kevin Blair]

Hi All,

Finally have the capital raised to do a flip where total costs do not exceed $160k. I found an SFR in a nearby suburb of Chicago I like and am attempting to get the highest quality comps possible. I did have an agent send me theirs, but I have issues with two of the comps being used and I'd prefer to do my own comps as well just to make sure I'm not being "sold" on a property that isn't actually that great of a deal.

The house I'm looking at is a 3/2 SFR, but I can only find one comp I actually like that is also a 3/2 SFR. The next best two I can find are a 4/2 and a 4/3, unless I'm willing to look at properties sold 12-18 months ago. All these comps are within 200 sq. ft of eachother and I'll be using the square footage method to get my ARV

My question is... is there a reasonably reliable way to adjust the sold price of these homes based on them having an extra bedroom and bathroom? For example, should I knock $10k off the sold price for the 4/2 comp I'm looking at to get a better expected ARV? I know appraisers have a system similar to what I'm talking about, but I don't know exactly how they add/subtract value from comps to get their appraised values.

Thank you all in advance!  I look forward to being able to be more of a "contributor" on BP in the next few months than a "taker."