You you do not want to spend months trying to build up your company buy one. But then your at the deep end.
Get a small resellers, start one up. See if you like doing hosting then buy out a company.
Or work with another hosting company as a support tech. Or for free for a few months then buy a company out. This way you can learn every thing about hosting before crashing into the deep end of the pool.
I would say it's better to start your own because it's kind of like buying a house. You don't want to pay for someone elses problems. I would recommend that if you do buy the company then sign up anonymously for a hosting account and find out first hand how they treat there customers and such.
Buying an existing business would ensure you have a level of income from day one from the existing customers. While if you start from fresh, you have to compete with the rest and there is no guarantee that you will have the same results.
Then again starting from fresh you will give the business your personal touch and if you do buy from an existing business and they do not quite treat their customers well then you will be in trouble trying to fix issues.