I would go with a Creative Cloud subscription. Take a look.
I have a Complete one, because I use more than one of their applications and I have steady clients that justify the monthly expense, but if you need only PS, then it looks like 9.99 would do the trick.
Will my files be hosted on their servers?
No. You can host them in your own station.
Can I buy a personal subscription and use it for business?
I believe so. The business subscription is designed to help businesses to save money. It is like buying in bulk. This does not mean that you cannot use the personal ones for business. I have a personal one and use it solely for business. My main client has 4 designers in house and has a personal license for each one of them instead of a business one.
Are you sure sure sure I can use it for business?
No, I am not. I am not a legal adviser : ) I am using it for business, though, so at some point I guess I did the research. I can't find anywhere in the web where it explicitly says so. Something you could do, though, is to try to buy a personal license. In the process, you will be presented with the legal terms and you will have to agree to them before proceeding to paying. You can give them a thorough read. I would think (don't take my word) that if it does not say explicitly that you can't use it for business, you can. It would be like renting a camera. You can use it for whatever you want unless they told you you can't use it for business and you agreed to it.