There are so many things to consider before you start a business in your home. Liability, which PaperPrincess mentioned, is a big issue, and your homeowner's insurance probably will not cover you for liability or damage to your longarm if you are using it in a business. You also may need a business license, and you have to keep records and pay taxes. In Oregon there's a property tax assessed on any equipment used in a business - not a high tax, but it requires keeping records and filling out forms every year, even if your equipment isn't high enough in value to require that you actually pay anything. If you make enough (the limit is only $400) then you have to pay social security tax and medicare tax on your earnings, and that is more than 15%. If you are already doing longarming professionally, then you have probably already addressed all of these issues and it would not require much additional record-keeping or expense to rent out your system, but it would mean that you would not have access to your machine during the time others are renting it. If you are not already using your longarm in business, then there's a lot to do and you have to decide whether that additional amount of money would be worth the effort. (The other worries - that you would potentially have strangers in your home, that someone might damage your machine, that there could be scheduling difficulties if someone doesn't finish in time and someone else has scheduled the machine...)
I think renting out time on a longarm is better done in a business location, although there probably are people who have successfully done it in their homes, and of course some probably do it in their homes without thought to the taxes, license, insurance, etc.