Most of the people I know who make their living by running a studio have a standard of living only slightly above poverty. I do know a few who make a "decent" living - but they are good business people who work with corporate clients and marketing agencies (if you depend on bands and songwriters you will most certainly die poor). In my humble (yet informed) opinion, anyone who wants to make a living in music has to have several things going at once: having a studio, writing jingles, doing gigs, teaching, maybe working in a music store, etc. (cause if one gig falls apart, you need other things to support yourself).
I was a full time musician for several years (at that time I was just a road dog) - and even in the good years (Vegas gigs, etc.) it still wasn't a decent lifestyle - but I was in my 20's and the priorities were: sex, drugs and rock & roll (notice no mention of food, or rent).
Even though I now have a "real day job" - my personal policy is (and always has been) my gear must pay for itself, within 6 months (after 6 months it will probably be obsolete anyway). I don't buy a piece of gear unless I know I will have clients to use it (or I can use it on a gig). However, since I am a gear slut to the seventh power, I still gig several times a month and work part time in a drum shop - so if the studio has a dry spell, my other "music related revenues" will pay for the gear.
I guess that makes me a 2.