Revenues below a certain point aren't worth forming an LLC around. For 125k it can be worthwhile ,though.
You need to be registered in both states. So, you should look at the SOS site on both states and find out what the costs are for each state for:
- domicile/formation of the LLC
- annual fees (especially in CA)
- payroll taxes, etc.
- foriegn registration
Then just do the math. Probably it will be cheaper to hold the LLC in OR and then register it as foriegn in CA. I'd be willing to be on it Plus, it's just more natual and convenient to domocile the LLC in the physical location that you will operate it in unless there is some special reason not to.
In almost all cases, the pace where you operate the LLC is where you have to register it. So, even if you only have one client in CA you will still be servicing that client from both CA and OR. Check with a laywer for some nuances of these laws, but that's the general idea. If your client was in CA and you never went there, you probably wouldn't have to register in CA at all.
There are some tax gymnastics that you can use to get around these things, but they aren't that simple and at that revenue level it's probably easier to hire a good CPA and just let them deal with it. But, avoid CA taxation as much as legally possible!