Songwriter - producer
If you are a writer with your own production company you will be able to tout your services to record labels or artist management. For a fee plus a share of the royalties you will deliver a hit Pop or R&B song, or Dance tune, ready for release. Actually almost ready since undoubtedly the label will want a remix.
You have to be a good writer, but you don't necessarily have to write great songs. If you are a songwriter sending out demos, then your songs have to be great until you get signed by a publishing company. After that you can relax and write the occasional great song, interspersed by many of simply 'professional' quality. You hear them all the time and you think, "I could have written that". Well you probably could, but who wants to listen when they can get all the songs they want from publishers and production companies?
Inevitably, top class artists will want to co-write. What this means is that they have half an idea, you do 98% of the work and you share the royalties equally. Who said that the music industry was fair?
The equipment you need...
Basically the works. You need a world class studio set up, including sound proofed premises with parking, kitchen, toilet, acoustics and everything. The equipment will be the latest and the best. And there will be just so much of it that most of the money you make, even from top 10 hits, will be used simply to repay the finance.
Having your own production company, basically, is what you do when you have already seen some success. You reinvest in your own studio in the hope of becoming even more successful. Mind you, many people have done this and a couple of years later seen the whole thing go down the tubes. Then they think back and realise that they could have bought a house for cash...