1. space: you need room to store at least two 23-litre containers, space equivalent to a third one to store the ancillary equipment, and 30 wine bottles.
2. strength: you have to be able to lift a big glass jar containing 23 litres of wine from the floor up to counter height. It's around 27 kg, or for you furrinners, about 60 pounds.
3. individual taste: if you like sparkling wines or champagne-type stuff, it's a little tricky to get right and not everybody has the patience to do it. Still wines, however, are quite simple, and with the easiest kits takes about 3 hours of work spread over 4 weeks.
4. chemical sensitivities: the standard sterilizer (and you have to keep everything *REALLY* clean or you'll end up with 30 bottles of vinegar) gives off hydrogen sulfide gas in small quantities. You can't avoid contact with it. There are other sterilizers, but they're essentially soaps, and the equipment requires endless rinsing to get it all off.
5. patience and care (hinted at in the previous point): it's not difficult, but you have to do it right and be scrupulously clean and careful. If you're a pig, a slob, impatient, or stupid, don't even try, you'll just fail.
None of those are issues for me, though #2 might become one as I approach old age decrepitude, which I hope is at least a couple of decades away yet. But then I'll build some hydraulic lift apparatus to do it for me...