FAQ from their page
The FAQ at the site has a pretty complete set of answers for you.

"Is my ordination legal? This is the most common question received by the Monastery. Rest-assured, your ordination is legal in all 50 states. As for performing marriages: yes, you are legal to perform marriages. In some states, registration beforehand is required. You can call your local County Clerk to see whether or not you need to register. There are some states that choose to take issue with registering ULC ministers. This is their ignorance, not the law. It is acceptable, when filling out your registration and the actual wedding license, to put the phrase, ‘non-denom’ under the section ‘denomination’. If this is unacceptable to the Clerk’s office, they will let you know. This may help avoid any conflict with people who doubt the validity of your license."

"As a Minister, what tax exempt privileges as I allowed?

In most cases none. As a private citizen, all your earnings are subject to taxation. Some states do allow an exemption on private property for the clergy. Check with you local Assessor."
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