Mark Zilbert sells condominiums. In April he will have been in the business one year; he will have sold almost $20 million worth of real estate and earned himself an income in the high six figures.

If you approach him with less than $300,000 to spend, he will politely direct you to a colleague, because you are not worth his time.

Nothing against you, personally. It's just the potential return is literally not worth the investment of his time. Zilbert is strictly a luxury guy.

The client was on his way. Dr. Jeff Rubin. Young, a healer or perhaps scholar of some sort -- exactly what he did for a living Zilbert did not know or care.

The crucial details of Dr. Jeff's existence were two: he was rich and he was in need of a South Beach condo. Something fun for the weekends.

Some months ago, according to Zilbert, Dr. Jeff had called him. ''I hear you're the guy,'' he said.

''I am the guy,'' Zilbert may have said, or possibly something more neutral. ''Well, I'd certainly love to help.'' He doesn't remember exactly. Doesn't matter. The client was on his way and he wanted to buy.

Zilbert leaned forward in a couch in the lobby of the Murano Grande, 400 Alton Rd. South Beach has no Fifth Avenue, no storied old-money co-ops overlooking the park. Instead it is specked with new high-rises like this: the lobby ceiling 30 feet up, fountains burbling somewhere in back, a spray of orchids in a glass vase on a glass table. A woman came by to spritz the orchids and then vanished.

Zilbert, 39, is a mentor, a friend, a facilitator. Just now, though, he was talking philosophy.

''I don't care what they do, where they come from,'' he said. ``I hook into their desire. There will be a sale today.''

He wore loafers and a blue blazer and a white shirt, Prada. His teeth were brilliant and he did not stop smiling.

ANOTHER ON THE LINE

He took a call, a prospective client named Patrick -- Zilbert used the name at every opportunity -- and Patrick made him very happy. Zilbert took the necessary information and promised to call back later for an in-depth conversation. ''You're in good hands, Patrick,'' he said, and hung up.

''This will turn out to be a sale,'' he said. ``Four fifty to five hundred is what I'm thinking.''

This was not a boast but the statement of a reasoned hypothesis based on -- based on what, exactly? ''You start to see patterns evolve,'' Zilbert said. ``There are certain cues in the words they use, the energy level in their voice, especially in the first 15 seconds.''

A late-model Mercedes, black, rolled in. The valet sprinted. Zilbert stood. Dr. Jeff had arrived.

He was a man of average height in a white Izod shirt, cinnamon-colored linen pants and matching suede loafers. The amazing thing about him was his arms, which were thick as trees and utterly hairless. Also, he had an incredible tan.

''How do you get a tan like that this time of year?'' Zilbert asked.

''I vacation a lot,'' Dr. Jeff said.

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