Newbie needs help analyzing a specific Property

[Mitul Gandhi]

I am working with a realtor on my first purchase. I told him I only have 15K to put down and needed help finding different ways to fund it. I am a first time home buyer so I can put the 3.5% down with an FHA loan.

I am looking at this property here 3928 N Bernard St CHICAGO, IL 60618

I was hoping someone could help me analyze this property .  

I was trying to use the BRRR calculator but im stuck at estimating ARV -

I'm having my realtor pull comps for me right now. I downloaded the ARV estimator word document- one thing I didn't understand is how do you know how much to adjust upward or downward. The example he gives is subj house is 1940 SQF while Comp is 2650 sqf he subtracts 8000 from the comp.