How to turn my passion into a small business?

I can do repair jobs easily, but it would hard for me to get clients by working at home, moreover no one would trust a 19 years old easily.
I can do the job of repairing amps and monitors too, refurbishing would be great thought, I can buy old or broken amps and repair it or make a whole new board and sell it online. But how will I promote it online, half of the people will go away by looking at the word refurbished? It will be a little hard for me to make connections in the local market.
Or, will it be helpful if I make the boards of amps, mixers etc and sell them online without the chassis? Because making chassis will also be a hard job for me. Or you can tell me how I can.

-Thanks

Repairs are more or less just a good way to get your foot in the door, and always a good service to offer on the side. As for the refurbishments, musicians are always looking for good refurbished material. Like I said you need to come up with a business plan. The best way to become a great business is to pretend you're great until you don't have to pretend anymore. Get a facebook page started, promote your posts, and once you've grown enough look into getting an official site. Sometimes a better word for refurbished is "custom." It may sound shady but if you're product is good that's all that matters.

I needed to hear this word "Sometimes a better word for refurbished is "custom"".
Thanks that helped me a lot.

I was thinking of starting both business. I want to run the online website too because both have pros and cons for me.

The online website cons is it would draw me customers like students who are like to buy less and I will make less profit, and it takes too much time to get some profit from websites and pros are that I can keep myself in my comfort zone like working a home and working anytime.
On the other hand if I do the amp selling job it would draw me high value customers and my profit will be quick and cons are that I will need to go outside in local market to find customers that is a hard job for me, and making chassis is also out my comfort zone.

Am I going the right direction?

It sounds like you're getting your plan together. Starting a website can be rather expensive, unless you can build your own efficiently. I just recently got into graphic design and web development myself and it's no simple feat.
Facebook on the other hand is a very cost efficient foot in the door as far as getting your name out there. Just remember, you don't have to limit yourself to one market with a skill like this. Music is just a suggestion. I'm a musician and I can vouch that there's a good deal of money in the electronics aspect of the industry, however, I would make a list of your top 5 or 10 skills in electronics.
Figure out what it is you do best and try to determine your best options from there. Stay within your comfort zone, while you're starting out and take it from there. Try and make yourself a business plan, and browse your area to see what sort of prices you're competing with. If you can offer competitive prices and great service I'm sure you'll do well. And that's about all the advice I've got. Good luck, I hope it works out for you!
-Jake Social Overseer

I think musical field electronics is the only option for me now, so I may start with it, later if I find something else more profitable I will make that too.
I good thing is that I can adapt to any small electronics that can be made from scratch, like I can make 12V to 220VAC converter, I can make home UPS system, maybe some security products. But I will not be able to get hold of the clients that will buy these. Any another big thing is that all these things need good chassis, I can't make that.
I am also a musician so I think this will be good for me.