If anyone knew the answer to your question there would be no employees and we would all be rich doing our own thing! That being said you first need to come up with a business plan as to what your actually selling a product or a service etc. If your trying to be a consultant then you need to identify a Niche area where your expertise is required. The way I started out was to target small contract jobs and once you have built a client base you can offer to sell/develop larger projects. Cold calling for development doesn't work but it does work for admin work. For payments you need to break it up and get something upfront, it will be tough at first but once you start getting 25% of your money upfront consider your self arrived. So its something that you need to experiment with there is no one way to do this. But now since you have taken the plunge enjoy it .

The best way to prepare for an interview is to put yourself in the interviewers shoes and imagine what you as the interviewer would do? That being said I would look at a few interview questions on the internet for .Net fundamentals, SQL Basics and reporting

The best way to do what you have requested is to use Threading.Timer as you have already noted. Timers aren't meant to be used this way though, that is to wake up at a specific time only. Why don't you use the Scheduled task if what you want is to run your service/process at a specific time.