lots of good advice above, i'll add my own 37 cents from having tried this a few years back, and still having it in my long-term sights.
1. choose your "partner" (s) carefully. when money is on the table $hit changes.
2. get practical experience BEFORE you open the doors. you cant charge a customer for your learning curve.
3. do it as a legit company, set up an LLC, get insurance, etc... mainly to protect yourself financially. but if you work out of your garage and undersell the legit competition around you because you dont have the hassle and expense of things like insurance and such, you will not be well liked, and when you do become a full-on business you will hate the shadetree guys because they are under-selling you.
4. make sure you are walking into it understanding that YOU arent worth the $xx.xx per hour you are charging the customer. the business is. not you. pay yourself out of that, but NEVER lose track of that fact.
5. the majority of your business will be one-time newbies. Jeepers tend to turn into DIY junkies as soon as they realize they just paid you to do something that wasnt that hard to do at all.
6. unless you really come up with some amazing new design that is impossible to copy, don't bank on your own "unique" design abilities to bring in the bank long-term. there are pre-bent and laser-cut kits for damn near everything available these days. use them and make $$ on the fabrication and installations.
7. take the regular work that is always available. fabrication and modification work slows down in the summer and around the holidays..
8. get used to peanut butter and jelly sandwiches. real meat will not be in your personal budget for a long time.
9. DO NOT SET UP A RETAIL STORE. you will not be able to compete with on-line sales prices. you can set yourself up with a catalog "showroom" so you can order stuff in for people and take a small comission, but the cost of buying-in with a vendor just to let inventory sit on your shelves will soak your wallet too deeply.
10. lastly, be realistic with yourself about money.... dont allow a business to kill your personal financial stability. you either arent making enough to sustain the business, or you are keeping too much for yourself.
take the time to go to the shops that are open here in new england, talk to the owners and guys who work for them. most of them will give you solid advice about mistakes they have made.
good luck,
