Have a look at job sites to see what a salaried position with your experience would get you. Use that to work out the hourly rate you would be paid and add 25-30% to cover your expenses for the time you spend on admin tasks or tasks that don't bring in any money. Multiply your new hourly rate by how long you think it will take you to complete a task. Over time you'll get better at estimating your time.

If you need to purchase something for the project I generally sell it to the client at cost and work the cost of the purchase into the overall price. Most clients would expect you to add a markup to purchases but they're pleasantly surprised when you don't. You still get your money and you get a happier client in the end. Everybody wins.

However much you need for your business model to forecast a future you would be happy with.

So if contracting, enough to cover your cost of life, either from the outset or taking into account some forecast of growth due to experience or ability to scale. The more forecasting involved, the more frequently you need to evaluate it.

Sorry, I know not that helpful - but I do mean it with sincerity. It forces you to think of the fundamentals and avoid expensive wrong turns.

It depends on what services you are providing. Try looking at the market and see what your competitors/peers are charging for similar services that you want to sell, it's a good starting point.

In theory you should try to charge as much as your clients are willing to pay for your service. That might be very different amount based on how valuable the service you provide is to them.

Here's a list of methods to choose your pricing: https://taprun.com/methods/

If applicable, I like to charge such that the implemented system will pay for itself within 24 months.

Every time I start getting a lot of requests for work, I up my price. Ideally you should be getting about 3 requests for work per month. 4 is pushing it, it means you should be charging more.

Charge more until you stop being flooded with work requests.