[carlosjobim]

> they now expect support and maintenance for me.

In worst case you give a refund if the software doesn't work as promised for the customer. You're not forced to fix bugs or problems that are beyond your capability or interest.

Taxes are not a big deal and can be ignored until you start making decent money on the business and can afford your accountant. The taxman understands and is not going after people in the starting phase.