Legal issues to include software licenses
We don't install trial software for the customer unless it is our own software. I.e. RMM stuff.
We don't work on pirated software. Period.
We charge hourly for troubleshooting any kind of share-ware, free-ware or open-source (i.e. thunderbird, etc.) as long as it isn't trial-ware.
We don't work on trial-ware.
We do this for licensing reasons (that EULA thing). If they say "my pirated version of Windows" or "my pirated anything", I won't even open a ticket or entertain them past "have you considered purchasing the software?" If there is pirated software on their computer, we inform them, and work around it. Work within the EULA.
Other legal things should be covered in your Terms of Service, i.e. what your liabilities and limitations are. This is very important.
Permits
State-to-state, county-to-county, city-to-city. They vary so widely. More than likely you'll need a Transaction Privileged Tax (Sales Tax) License at the bare minimum. Even if you don't sell anything other than services, but because you buy hardware/goods for your business online, your local area (city/county/state) my say you have to pay a useable tax.
Other permits might include low-voltage, or a general contractors depending on what all your business provides such as running Ethernet cable from one side of the building to the other. We aren't that regulated of an industry, but sometimes we cross other industries lines, and therefore need one of their permits or licenses.
Being bonded helps a lot. It doesn't matter if you get bonded for a project, or because you deal with multiple managed clients. Bonding helps protect you and your client. If you don't perform your job, and the client has losses and comes after, the bonding will ensure they are paid for said losses. It's kind of like insurance, but it is far from it. It also makes you more appeasing to their eyes, cause they know if you fail to do what you said you would do.
Company name
Varies on how this is handled. At a minimum, get a DBA if you use any name other than your own. Like us for example, we started out as a DBA to get the ball rolling, and while we waited for our LLC to go through the AZ Corporations Commission. The DBA locked in our name by tying it to mine. So when the AZCC went to make sure the name was available for LLC, it was easier to obtain. There is no guarantee you'll get it, but as long as no one else uses the name you are more than likely going to be okay.
Everything that's your businesses needs to have your businesses name on there. Very important for an LLC, Inc., etc. Insurance, banks, bonds, etc. Nothing is in my name when it comes to the business. It's all in the businesses, like it was its very own person.
Guarantee on services
90-days is typical. So is 30-days. Your call, but make sure the ToS covers them, or have a separate guarantee document. State what is and isn't covered. Many people don't read what's going on, and try to bring it back on you. If your warranty is pretty sound, and within the legal constraints of the local governments, you might make it out of a court room alive.