Is it possible for him to invite us?

Cheri, because he doesn’t have residence permit in PRC, I’m afraid he cannot invite you.
Actually, if you apply for tourist L type, you can provide round trip air tickets and hotel reservation to replace the invitation letter. In this case, you just provide the required documents including your passport and copy of its data page, the completed application form affixed with a passport-style photo, proof of your financial support, round trip air tickets and hotel reservation. And then submit the application to the embassy of PRC to apply for it.