As a rookie, what year built should I avoid?

[Mike Schorah]

I'm trying to do a BRRRR, but I don't want to do a full gut rehab. Should I avoid houses built before 1970? 1960? 1950? I know that money can be made with full gut rehabs, but I also know that rookie mistakes are extremely expensive with full gut rehabs. I want to avoid houses that are so old that, on average, they'd require a full gut rehab.