Czech Schengen Visa

Hello, I would like to hear any advice on our situation. My bf (Indonesian) is currently living on a valid visa in Australia, therefore he will apply for a visa in embassy in Sydney. His plan is to fly to and from Budapest (its cheapest). The rest of the time of his trip, he will stay at my place in Czechia.

Should we mention this in the application and itinerary? I read some advices to not to mention any friends / partners. Our first plan was that he will not mention me at all. He will book hotel in Prague, and later after he gets visa, he will cancel it. But now I read that if the visas are granted and you cancel the hotel bookings, they can refuse the visa. We will stay in a hotel only in Budapest and then for Czechia, no hotel is needed.

Or should we present the thruth, that he will stay at my place? What kind of documents are necessary to provide from me? Would be passport, cover letter and my rental contract enough?

Im scared mentioning that he will stay at my place will weaken his success rate.

Thank you.