Staffing the Model and dealing with the required staffing hours which are out of sync with the rest of the World(almost like being a Shift worker).

Yes, agree with all answers. 

Finding enough listings.

Knowing when to be there and when to take a break. 

Creating the needed volume of traffic is always a concern.

if you have good relationship with the on site people, your only challenge will be how to spend your money.

People look around and signin since you do not watch them like hawks...

With the technology few home buyers even use buyer agents anymore. They look on their own strike a deal with listing agent. 

marketing consistently enough to keep the energy fresh and flowing.... a flat line community is 'dead in the water'

Currently; few pay commissions or referral fees to Realtors due to their selfish fair-weathered friends position. We bailed them out in the Great Depreciation, but now they are back to "min, mine...all mine attitude".

Also, they try to steal buyers who "walk in unescorted". I use a BRE, it was awesome to watch them pay or lose the buyer back in the days when I supported them.

I no longer support them with my buyers.

Has never been a problem. The biggest issue is customer registration!