I like Evan’s post above, good advice. I would add that you should avoid any properties with major uncorrectable deficiencies which will reduce your buyers pool thereby reducing profits. Examples are next to commercial, on major streets or near freeways with traffic noise and smog, no garage (unless the entire area has many homes common without them), near railroad tracks, in airport flight paths, too many stairs to climb to front door, etc.
The level of rehab should be factored in too. If the rehab is heavy, your hold time will be longer so make sure to account for that. Also pay close attention to the surrounding homes. Is the subject property sitting next to another dumpy looking house? Since you can’t fix that one too, proceed with caution as most buyers will not want to buy a nice home sitting right next to or across the street from these dumpy homes. Of course not all markets are created equal so take that into consideration regarding my advice.
Knowing your market conditions and trends is also of vital importance. Since you have already done 2 brrrr homes, you probably know this already, but since you have not sold them, you have not actually completed a flip, just a remodel and the sale piece is an important step in the process. Miscalculate and pay the piper.
I look for the ugliest most outdated home in a nice area with other nice homes on the street. These tend to be the very best in profitability as they typically sell fast if you did the job right. Depending on your location and market conditions, buying the smallest home (perhaps a 2 bed 1 bath) and adding on can also be highly profitable so long as the cost to build the addition is well below the cost per sf you get at resale.