I am interested in creating a few software assets for myself, and for that to happen I need to own the software I create for the clients and license usage to them.
What kind of arrangement - legally - am I looking at? Partnership? Licensing?
If you've finished the software and are not heavily customizing it for a client, then I believe that is more of a licensing plan. Just sell it. Again, lawyer.
I would not mess with a partnership. I don't have a good reason for this, but it seems to involve tighter coupling than I'd want.
Note: I'm not a lawyer (but I have sold semi-custom software to companies, without a lawyer; I would do it differently now but it worked out fine).
You may have to consult an attorney to write the contract so you own the IP and grant a license to the client. The client may ask to pay for the license rather than pay for your time to write code they don’t own.