Well I mean, right now it's tough to build a rig at all with all the gpu shortages, and the premiums you're going to pay for your hardware are pretty big, meaning your ROI will be slower because the initial setup cost will be higher.
That said even at current prices a 6X3060Ti rig is pretty easy I mean R3k for board/cpu/ram then another I dunno between R200 and R2k on a suitable case if you want or just build one yourself even better make sure to budget at least another grand for extra 120mm fans if you go this route. And of course big PSU, the BTC ones are like R1600 - R2.5k still. Then ya the cost of the GPUs, currently R70k for 6. Ballpark. So that's R80k upfront for the build cost, machine like that will draw around 1200W from the wall and probably run you just over a grand a month in electricity costs although if Eskom has it's way which it always does that'll soon be R2k/month in juice.
6 cards gives approx 360MH/s on Eth. That should roughly net you say 0.7 - 0.8 eth / month. At current price of Eth that's I dunno like R24k. So yeh, probably worth it.
But and this is a big but, the thing is it's volatile as hell. It's unlikely to hold the current rally prices for long (although tbh, this current rally is very different to previous ones because of all the institutional guys coming in so....). So if you pay all this money up front and get setup and ready to go, it's quite possible that the price will have crashed back down to the USD200 or even USD100 level (possible - not likely in my view, probably be seen as a worst-case scenario) at which point now your 0.7 eth/month is worth like R2.5k/month so now, suddenly, not worth it. In which case just about your only choices are sell up your hardware and move on try to recoup the costs, or just keep on mining and hodling till the price goes up again. Which, obviously, it will eventually, being a cyclical data system. In oh anywhere from 6 months to three years.
Definitely a gamble. Just trading might be better, but I would wait for a dip before buying back in to the trading game. Buy low sell high is the only rule there, pretty simple but time it right and very lucrative of course. Also a gamble I reckon but hey. The philosophers will tell you waking up in the morning is a gamble.
Recommendations: Buy the best GPU you can afford new, and make sure it's got a good locally-supported warranty in place so swapping out is hassle free when the fans do fail. After that yes fixing fans isn't too hard or too expensive but ya then your maintenance does go up. Avoid dust. It kills electronics, especially electronics that are on 24/7 and get really really hot. Obvious stuff you know? Motherboards I mean there's all the options in the world most gaming boards will do this stuff with the right risers etc but the Biostar B250s are probably still the most common, you get 6-GPU, 8-GPU, and 12-GPU versions of that board for very reasonable prices.
As for GPU, a lot like with gaming it's really your preference. NVidia cards esp the new generation are monstrous with their hashrates, but are a bit more limited in terms of algos they work well on and I dunno my 1080s always thermal throttled when I did try mining on them even at 60% power and temps never exceeding 70deg - something weird in the nvidia driver which I know some people said they could get around and yeh some of those workarounds did work but still they were never as hassle free as the 580s, which just plug away at Eth like well little machines provided you know enough to at least have flashed a decent mining bios onto them for the tighter timings.
If you're not all that comfortable with hardware and building and maintaining things, there are plenty of places that will supply you with a prebuilt machine just plug in and go. Bit more expensive of course than building your own but some nice stuff available. Or just contact someone who has been doing it and get them to help you out directly. But it's no get-rich quick thing. That's more like the ultra lucky traders who buy in at like USD9k and then watch it explode up to USD50k in like a month, or the long hands who bought in way before that mark even.
