The best research, the best content, the best value to the attendees, the best event structure to maximize attendee engagement, and the best presentation. 

Most of the attendees own multi families or are in the process of acquiring them.  

Renting rooms can be lucrative but it is a major cat herding proposition and you are renting to people with many times no better options,  so expect constant drama and only consider this if property is close to a college/university or some other major institution that attracts a lot of transient attendees/employees, like maybe a hospital. 

One of the attendees mentioned that she is having no problem finding houses.

I researched reviews about them and BP was on another attendees review. 

This allowed the attendees to get more attention than at an event hosting 100 people.

I havent been to any meets before so not sure what would work best in terms of number of attendees, cost\budget for the place etc

The attendees keep going back so just networking with the other attendees is worth the seminar as most of them own hundreds of properties.

The jargon and presentations went far over most attendees heads.

One of the attendees, who is also a client, is consistently sharp (Well, actually, most of the attendees were; the average bear does not take time & money to attend such an event.) and asks good questions.