A few tips:
1. Don't work for people unless you can help them make a lot of money.
2. Avoid freelancing marketplaces. These tend to have terrible rates, small projects and some of the worst clients. Most of these clients cannot be helped to make a lot of money no matter how good you are.
3. Do not charge an hourly rate. You do not want hourly jobs. Charge either a daily rate, a weekly rate, or a project rate. If you have a good client who regularly needs small tweaks, charge a monthly retainer instead of an hourly rate. I'm told that some really smart consultants charge a percentage of the of the improvement they make for the business.
4. Require half payment up front, or for longer projects, a milestone-sized payment up front. This will immediately eliminate all the clients who are allergic to writing checks, and I've never seen anybody serious reject this.
5. When setting your daily or weekly rates, plan on charging at least 2x what you would receive as salary, or up to 3x in some cases. This depends partly on the average size of your projects. If you charge less than this, your annual income will wind up much lower than you'd think. You will have lots of downtime and non-billable hours.
Aside from all that, one big challenge is balancing your pipeline. You'll have 2 months of no work, followed 3 simultaneous offers for highly-paid jobs. You need to find a way to manage this that's fair to the client and sustainable for you.