I have been wrestling with the idea of opening a commercial studio for the past two or three years now, checking out potential buildings, writing down different kinds of business plans, calculating possible expenses and income, discussing loans and funding with banks, talking to people who have been in the business for a while and so on, and I'm slowly coming to the conclusion that going that route with loaned money and/or risk funding is a total financial and mental suicide. I have been to several decent studios that are struggling to stay alive, and honestly, I'm pretty sure they are going under in a matter of years unless things will change drastically and fast. Perhaps I'm being cynical, and I'm sure this varies on a regional level, but that's all based on quite extensive personal research.
I have to choose between going full-time or finding a job in some other field of work in the beginning of June, and from my experience I feel the most risk-free and manageable solution is to concentrate on running a small mixing and mastering studio while picking up freelance engineering gigs at commercial facilities when possible. Minimal overhead, large potential customer base and being able to keep rather reasonable rates are things that make that solution feel like a pretty decent deal to me.
I'm sure the DIY-trend will lose it's appeal in time, and it's totally possible that I will change my opinion in the future, but right now I think the keywords of being a full-time AE are "minimal overhead" and "versatibility."