Persuading national tenants to deviate from their customary design format required "lots of negotiation," Mr. Oliver said.

The big thing, clients say, is that they do their homework, often persuading tenants and landlords alike to look beyond the rent numbers in their deals.

Persuading tenants to cooperate is a key task for the entrepreneurs.

Rockefeller Center, for one, spent much of last year persuading tenants to renew leases.

But like in so many previously industrial areas in Manhattan, the critical shortage of office space elsewhere is persuading upscale tenants to move in.

With revenue coming instead from sponsorships and commissions, their challenge has been to persuade building managers, tenants and brokers to use the services that generate fees.

The Coalition for the Homeless, meanwhile, hopes to persuade commercial tenants and managing agents to cooperate in mounting efforts like Common Cents in office buildings.

"We persuaded tenants that they should be near the people they sell to," said Sidney Winoker, Winoker Realty's president.

Instead, after a complicated lease negotiation that involved persuading other tenants to play musical chairs with space, Friedman expanded within the G.M. building.

Mr. Lorberbaum often persuades tenants who need more work to buy rather than lease.