Has anyone heard about a portion of the condo units, says 30% of the total units, is being operated like a hotel as the owner purposely buys them and convert into a hotel ? What is the implication to the remaining condo residents ? What are the pros and cons ?

Serviced Apt/Suites such as Maytower and Times Square are operated and advertised as hotel plus the fact of commercial status. However, some wealthy owners in Savanna Condo Bt Jalil bought a number of units and convert them into hotel for short term or long term or even daily! Savanna is definitely a residential condo !

The biggest concerns are security issue, potential higher maintenance and possible illegal activities.
Anyway, the fact is condo is condo, hotel is hotel. Residential is residential, commercial is commercial. Problems definetely will arise once they are mixed together.
In the past, product like condotel was sprouting in resort areas, one of which was Costa Melaka. I don't know its status now as I have not been there for a long time.