For me the biggest barrier, in fact the reason I won't even consider it, is the idea of shoveling 3 hundred pounds of grain out of a mash tun. I may be a Gymrat, but I am an old broken down Gymrat, and I am just plain too old to be taking up that sort of thing.
Depending on the layout of the brewhouse, the amount of physical effort does not have to be all that great. I am 60 years old and I am the sole brewer on a 15 bbl system. The malt bill can range between 900-1600 lbs, dry weight, depending on style brewed. I run a very manual system where grain out is all done by hand. It is not THAT hard. You are pulling the grain straight out the manway with a hoe. It takes me about 15 minutes to empty the tun into containers supplied by the farmers who take away the grain.
All the other work is done by pumps.
The biggest barrier is that most people in a start-up can't quite understand that you get what you pay for. Too many are trying to get into pro brewing on the cheap. Looking at inexpensive brew houses that do not have local support or readily available replacement parts.
We spent about $300,000.00 on our stainless. Then comes the glycol system, Steam generator, walk-in, refrigeration, bulk CO2 system, draft system, kegs, keg washer, malt mill and malt handling. Not to mention sloped floors, REAL drains, floor treatment, water filter, correct sizing or water and gas lines and electrical service. Then comes the cost of hiring professionals to install all of this.
Lot of people feel they can save money by DIY. Unless you also do this in "real life" hire pros to run the HVAC and electrical. It costs more up front but it will save time and money in the long run.
After all that is done, you have to sell the beer. That is the hardest part.