It's not advisable to build a mining rig right now, GPUS are out of stock in every store in my country and that's not the worst part, I bought my gtx1660 ti for 400$ each and today it's 640$, the fact is people even still don't mind buying this cards at 640$ each, are they stupid? I don't know but getting back ROI should be their most worries, I think it's now nothing but FOMO
If you're getting FOMO you have to be more considerate at the long term outcome, there is a lot factors that affects GPU mining, the rig itself costs much and to build an efficient one takes more, and you have to consider electricity, these two combined over what you'll get in mining can be sometimes ignored but in my country your mining needs to overlap just to gain few and the time just to get a decent profit is not likely the best thing to do in crypto.