Do I have to register my company in each state where I have a client, or can I gain the benefits of registering in Nevada for instance, while living in Illinois, doing work for a client in Georgia?
1. Context aside, it depends on the business and the state and the scale of the business...and also the locality because local business taxes are also a thing in many places. Probably the biggest factor is scale. Someone doing $10k of turnover a year probably isn't worth pursuing even if they are technically violating a the tax code of some state and/or locality. Doing $10 million might be another matter.
2. To me, energy spent on avoiding taxes is often misdirected. Getting more clients -- or even better -- better clients will usually provide much more bang on the bottom line. It's just that those things are hard and following rules and filing paper work is easy and avoiding taxes has warm fuzzies and lets someone brag over beers. But taxes are just a cost of doing business and profits are a better proxy for success than tax rate...I mean if you want to pay zero taxes, just don't make any money.
Good luck.
1. "can I gain the benefits of registering in Nevada for instance, while living in Illinois" - no. If you have an employee in a state, or work there, you have a legal nexus there. At minimum this means registering as "foreign" corporation. So it doesn't save you fees in Illinois.
2. As far as "client is in Georgia" - mostly you're not considered as having a nexus in Georgia. But California says "if you make more than 25% of revenue in California you have to pay some tax here" IIRC.
Nolo has good resources by people who actually know something: https://www.nolo.com/legal-encyclopedia/state-income-tax-an-...