You have a few options, but it depends on how far you're willing to go.
Option a) provide alternate verification. This usually includes LinkedIn/a call from a work number/ contact from a work email etc. Not all providers accept this, but I've seen a fair number who do. Of course if you do this they'll know exactly who you are (name where you work where you live etc).
Option B) use a "screening service" like P411. They'll ask for some identifying information (drivers license info, name, possibly employment) as well, but being an actual service it's likely to be more secure than giving the info to a provider, and supposedly they destroy it immediately after verification. Once you're "screened" look for providers who accept the base verification without provider referrals.
Option C) Find newbie friendly providers. These tend typically to be newer/not established themselves, and thus are usually more willing to take the risk. By the same token, you'll be TOFTT as they usually won't have a lot or any reviews.
External Link/Members Only --- use this site
External Link/Members Only Your question regarding agencies or independents......It doesn't matter, the review of the SP matters.
Choose a whore that has reviews - A provider with multiple reviews is more likely to be an experienced and safe provider, with an interest in her reputation. Many providers are reviewed on theeroticreview.com.
If she has a website --- good sign
Does she screen --- good sign
Reverse image search
she willing to explicitly talk about rates or services? Or does she try to get you to talk about these things? ---- red flag
Is her phone number associated with previous ads? If a Google search comes back with no previous ads or reviews, then there is a good chance that the girl is fake.