I can't say I really know, since I'm a music-school-dropout-cum-computer-jockey. I think that Vanderslice just kept buying more and more audio hardware to record his own music until someone said the obvious:
Dude, you totally rule at home recording. Why don't you open a studio so that other peeps can use your awesome hardware and mad skillz? He'd probably built up a library of connections with other musicians and engineers he'd probably lent gear to at that point, so he didn't have trouble getting initial bookings. And Tiny Telephone is definitely
booked: For roughly $600/day, including engineer costs, you can make some absolutely amazing recordings. I recorded a 5-song disc there, and although it's a total shithole in a bad part of SF, the experience was really, really great, and I plan to do it again, as soon as I can convince my lackeys^Wbandmates. (Side note: Survival Research Labs and Subterranean are housed in the same "complex" as TT.)
I have absolutely no authority to speak on the subject, but if I were interested in being John, here's the plan I'd follow:
1. Find a good home-base city. Chicago, San Francisco, or NYC in the USA will do. Charlotte, NC won't. Pay particular attention to cities with cheap-rent warehouse districts where you can make noise unhindered. Move there, ASAP, so that you can start to build up contacts in the musical world.
2. Find a musical niche. John's niche is "analog", kinda, but he started out digitally; his studio was Pro Tools-based before he saw the light, tossed it all, bought a Neve, and went 100% analog. This is a really great selling point for TT, since many musicians and engineers believe in the mystique of analog recording (including Mighty Steve Albini, who has an army of arguments as to why it's still better than digital.)
Of course, I'm not saying that "analog" is necessarily the "right" niche to be in now, but there are lots to choose from, and a "vintage" niche is often a cheap choice: Perhaps you can focus on vocal music and build up a great selection of mics, or maybe you can become known as the local version of Phil Spector/Wharton Tiers/Kramer.
In any case, a niche is essential. If the only thing differentiating you from thousands of other studios is price, you're gonna lose. In my opinion, a useful niche is backed by expertise, which takes time to build. Start now.
3. Invest in gear. GOOD gear, preferably a generation or two old, which'll sit nicely in a 19" rack, when possible. The better the hardware, the longer its lifespan, and you'll need to start buying now if you want to open your studio in 5-10 years. And quality hardware keeps its value, so if you decide to get out of the business later, you won't take a total bath.
4. Make friends. Lend gear. Keep your contact list up-to-date. The more people who simply know who you are and what you do, the larger your clientele will be when you open up shop. Be nice to these folks; don't just try to impress people with your technical knowledge. Communication skills are, in the end, more important than technical skills: When you have a hoppin' studio, you'll always be able to find very technically qualified engineers to work in it, but a great amount of technical skill without peeple-skillz won't gain you an initial clientele. I mean, who wants to work with an asshole?
5. Record yourself and your friends. Even if you don't charge them, their friends will hear your work and want to work with you if they like it. Plus, it's practice, and you'll gain technical knowledge of the hardware you use as well as expertise regarding which hardware is crappy and which ain't. You'll learn that what they told you in music school about cardioid placement is wrong and that a $1.00 contact mic has some amazing uses. You'll learn that you need to fake out some singers with a doubled dead mic. You'll learn that there's no substitute for a 6ft^2 plate reverb.
Again, I'm definitely underqualified to advise you on the matter, since I'm not an audio professional. The only qualification I have is in being 38 and having watched lots of my friends try to struggle to achieve their dreams in the wrong way. The US educational system, at least, teaches kids that they must spend X number of years in school; after they graduate, they immediately take a job in their chosen profession, and that's it. They live happily ever after. Nowhere is it acknowledged that some jobs cannot be attained via schooling only, but require much preparatory time and a wealth of skills that can't really be taught.
Two examples:
1. A friend of mine from in high school wanted to write comedy for films or TV. So when he graduated, he moved to LA with two other friends with the same inclination and proceeded to write and submit scripts to folks with whom he had no real connection. Naturally, nobody read them, and since they had no other means of determining that he was funny -- he didn't do standup or publish in other media -- he went nowhere quick and moved back home after 3 years. I don't think it ever occurred to him that the quality of his work alone wouldn't suffice to grant him the career he sought.
2. When I started university, many years ago, I wanted to score films. Of course, since it was a generic music school at a generic university, there were exactly zero classes offered on my chosen profession. As you've probably noticed, generic music schools train kids to be classical musicians or band teachers. The composition class I took involved a lot of instruction to "do what you feel like doing" and in-class listening of the students' favorite records, which ranged from Bach to Pink Floyd. I dropped out at the end of the semester, having quickly realized how incredibly foolish it was to think that I could get a "band teacher" degree and just go out and get a job for which my educational achievements "qualified" me. Nobody -- not my parents, my colleagues, or my friends -- had any notion that you had to get into the industry by the back door, that you had to have contacts, and that you had to had to labor in relatively menial positions alongside other folks in the industry before you'd have a chance at scoring a film. And I sure as hell didn't realize it.
I'm not saying that you're nearly as foolish as I was then, and I'm definitely not saying that I have the magic formula to success as a musician/engineer/producer/studio exec. All I'm saying is this: 1. Don't give up on the big dream, and 2. If the arrow doesn't fly straight to its target, look to see where the layovers are.