To start with you need to plan how much it will cost to set up. Consider every possible expense that you can think of and then add on some money for a contingency as things tend to always be dearer than you will imagine and it is likely that you will have forgotten some costs anyway. If you do not need the money then you will be able to pay it to yourself or just keep it to invest in the business when you need it. However, if you do not have any, then you may find that you need some and cannot get it.
It is also worth noting that it is unlikely that you will be able to afford to pay yourself for quite a while. This means that you will also need to make sure that you have some money available to you to use to cover your personal expenses. Even if the business has few costs and is profitable right away, it will grow more quickly if you invest back into it and this could mean that there will be nothing left to pay yourself with.
It can be easy to think that you can buy all sorts of things for the business when you first start. Whether you have a lump sum of your own to invest or a loan, it can be tempting to spend it on all sorts of things. Obviously there will be things that you need to start with, but try to be careful. Do not spend money for the sake of it but make carefully calculated decisions on what to buy and search around for the best prices.
You will find that once you get started you will be contacted by people selling you their services. This could be web design, graphic design, advertising and marketing, requests for charity donations and many other things. Some are very good at selling themselves and making you feel like you have no choice but to pay them. Think carefully about whether you really need their services, whether you can afford them and most importantly whether they are the right people to provide the service for you. Make sure that you get lots of quotes for work and only pay people for things that you cannot do yourself. There is so much information online that you can learn how to do many things and although you will not have the experience that the experts have, you may be able to find out enough to apply it to your business without paying out extra money.