Sure! The 25K limit is just for a single job. With today's prices, I think they are going to have to "re-think" that amount. I don't think most jobs are even checked for cost. Now if you take on large projects and have employees, even their labor is counted towards the 25K limit on each job. You would then need to get a contractor's (CE) license.
If you're just doing service calls and small projects, then you should be fine.
There are other rules for the business part. You would have to check with your city and county for the requirements. These would also include meeting the State requirements.