Hey there Dutchy. Im in the same boat as you. I'm a partner in the family construction firm. Although Im at uni I still help run it part time. When business is going well it pays dividends. When it has a quiet phase, it can be tough. Thankfully we have had a constant flow of work recently. A year and a half ago though, we had a few months where there was a slight downturn. Cash flow was a problem.
It certainly has pro's and con's. We work until we finish the job, and if we don't have another job to do, we have the afternoon off, funded by the previous job. When you take time off for holiday, you dont get paid. However, if it is successful the income should even out.
Know your market well. Thoroughly research it. Have a realistic target, and a time frame. Do the number crunching, and make sure it is viable.
If it is possible, test the market first before you make the jump and invest a large quantity of money and time. If you're overheads are high, and it doesn't work out, it will be a stressful period.
If you have done your research, and the numbers look good, check everything again. If you're convinced by realistic and positive evidence that it will succeed try it.
Sorrry I can't be a little more specific without further details of the venture., Hope this helps.