Hello @Stefanie Bergmann,
As far as Zillow leads, I would not recommend allocating any money here. They are very expensive, and Zillow will sell the same leads to you and 5 other agents, so they are not exclusive to you.
As for Facebook Ads, a lot of people complain and say they don't work, but they typically don't give them enough time to see results. I will say you will get a lot of False leads from FB, but they are so cheap that the volume ends up making up for it.
I run Facebook Ads for several Agent clients, and we are getting buyer leads for around $5-8 a piece depending on the market. It is more of a long term play with FB ads, as you typically only see about a 1% closing rate from these leads. But if you calculate the numbers to where you are spending about $500-1000 to close a deal, it is very affordable compared to other marketing methods.
It is all about the follow up systems and staying top of mind with all of these leads, as they are typically cold leads that are a few months out from making any type of decisions.