Tenant Won't Answer and I Don't Have Keys to the Property

[Andrew Rosenbaum]

I just closed on my first rental property which is a triplex in the Greater Philadelphia area. All three units are occupied with only two units paying rent. The third tenant who is not paying rent also happens to be in the largest unit. Ideally, I'd like to get him out first in order to renovate and re-rent it out to a new tenant. My problem here is that the tenant won't answer the door when I knock and I don't seem to have any luck with a response to my letters/notes either. I didn't receive any keys at closing as it was an off market deal and the seller's estate didn't have or couldn't locate any keys to the property. What should I do? I'm willing to do cash for keys which would be the tenants best option since an eviction will severely damage his ability to get another rental but he won't even respond to me and I have no way of getting into the property, even with proper written notice. 

The other two units will be tougher to evict as they are older tenants and with Covid running rampant, they are a protected people group so that could drag out for quite some time.