Using a vibrator and I just want to ask a few questions.?

I'm a gay male and I'm thinking of using a vibrator but I want to know if there are any health risks or some precautions I should take. Is there a limit per week I can use it? Should I put a condom on it? Should I use lubricant or is spit or something okay? What should I expect after using it? Will my get numb or swollen?