I used to fear this, until I read posts on a similar site about how frequently founders botch this and how understanding the IRS is with these situations. Obviously this only applies to the US. When I saw my first success, I paid a CPA ~$1000 (for hundreds of thousands in revenue) to help sort out the first year of taxes (before they were due) and it wasn't a problem.
To summarize someone else's better point: worry about this problem when you have it. In the mean time worry about problems you have right now.
To summarize someone else's better point: worry about this problem when you have it. In the mean time worry about problems you have right now.