I remember doing just this when first wanting to get a foot through the door... Offered to take on the task of building a website. I did just that and would go on to maintain, secure, and add new features for over a year.

The one thing I wish had been made clear to me beforehand was understanding just how little the non-tech and business savy people knew about what we do. As such, despite how much of a positive impact I had, my pay was not even close to what it should have been (first-year photographers were making more than me). It was a constant battle to explain why certain time was needed to complete various tasks, as well as why I was putting in the hours I had.

When I finally managed to get out of there, feeling underappreciated, it was THEN my once boss realized how lucky he had been. Nobody would come and work for the same pay while being asked to do all that I had done.

So be careful and at the very least prepare yourself if trying to go into smaller companies and businesses.