We have them at work. If you're buying extra hoops make sure they are compatible with your machine. I would also check the guarantee of your machine as using other makes' accessories may affect it.
If you're using it for a business then you need to source stabiliser, thread etc at sensible prices. So you would be looking at wholesale rather than retail. When doing it for a business you can't really be as fussy with things like stabiliser etc as you would if doing it for yourself. I have loads of different ones for personal use but that makes it pretty expensive for a business.
What type of service are you going to offer? If you are doing children's clothes etc you might need to look at rules and regulations regarding said items. Will you be digitising designs yourself? That takes time and needs to be paid for separately. As you have a seven needle machine, then logos etc need to be basic and try and stick to no more than 7 colours or it defeats the object of the multi needle machine and you will be wasting time changing threads. How are you going to structure your costs? Generally embroiderey is costed per stitch. But things like difficulty of getting items in the hoop need to be taken into consideration too. People often have unrealistic expectations about what can be embroidered. Things like Xmas stockings are often not possible and customers often ask for them to be undone and then sewn up again. Personally I wouldn't go down that route as customers don't really want to pay for that.
If you're lucky you may get a regular customer base. Firms that have tee shirts etc as uniform with their logos etc can be a good source of income when they wear out. I would always insist on payment on collection. No money, no goods. I have known at least two people lose out this way. One a company where one of the owners went to prison and the other disappeared leaving my colleague out of pocket by £200.
Word of mouth is the best advertising but you will need to advertise to begin with. Good luck!