** Shares of Bill Ackman's Pershing Square PS.N rise 4.5% in early trading

** Analysts kick off coverage with a range of calls, noting Pershing Square's durable, fee-driven model, though upside may hinge on performance and fresh capital inflows

** PS shares up about 50% since their April 29 debut at $24

** Pershing Square USA PSUS.N, the closed end fund, trading at $40.9 a share, down about 20% from IPO price

** PSUS investors received one share of Pershing Square for every five PSUS shares bought in the IPO

** Citi, among the lead bookrunners for the IPO, begins coverage with "buy" at PT of $50 and says firm has strong recurring revenues but upside depends on fundraising and performance

** BofA starts coverage with "neutral" rating and PT $42, says PS's model can deliver long-term gains, though risks remain

** Other initiations: Jefferies ("hold," $40PT), UBS ("neutral," $39 PT), Wells Fargo ("equal weight," $37 PT), RBC ("sector perform," $40 PT)