In all three possible scenarios (business functional role, Designer, Developer) you are going to have to hustle a lot more than you do during your current day job to make sure you have project work. Part of this is because you are your own agent and sales rep. You will also want to network like crazy, and not stop until you have so much coming your way that you don’t need to or until you have found several people who can refer business to you that they can’t work on or a larger company that will hire you full time. Attending related conferences (e.g. web design, web development, development (e.g. programming full stack web applications) will also help.
You should also get yourself set up with an LLC or S Corp and a standard service contract so that when you do work there is no risk to the client that you are their w2 employee. 1099 is often used instead of w2, but most stats and the federal government are not fooled. You and your client can get a painful and inconvenient reclassification long after the work has been done so it isn’t worth it. An incorporation itself usually runs around $150-300/yr (sometimes every other year). You should hire a lawyer to help you with this if it is your first time. Be sure to check back with at least once a year to make sure your contract does not need any major changes due to changes in local, state or federal law. Don’t assume your plain text reading arm chair analyst self can divine what the contract terms that you find on a site like doc stock will be sufficient. You will also need to file taxes every year which you should be able to do with the help of an upgraded version of Turbotax. A CPA could be hired for the early stages, but that is overkill – just use turbotax. You should also check to make sure if your county or state has a personal property tax requirement for your business (some states do, some don’t). This may require that you file an additional return that is not covered by Turbotax. The tax is usually minor.
Not everyone likes working from home. Ask people what it is like and how they cope or if they need to. A lot of people end up getting a co-working space membership to help make things more social.
Your best bet is to start doing this on the side long before you quit your day job to do it. It is harder and more complicated than you think it will be, but it has its rewards and can give you more flexibility. An even better option would be to find a company that is 100% remote or 100% distributed. One example of a company like this is Intridea. They are that kind of company and they have people all over the world working for them. What you don’t want to do is to try to convince a company that is not that way from the start to let you be 100% telecommute.