overall workforce, including sales and other employees? if this case, the 15months is highly diluted as sales force can easily years of bonus esp in booming property market.

or he specify it's on the IT line, more specifically, on this position he offerred. if so, try to negotiate to at least lock/gurantee a portion say 8 months (the number can negotiate up or down) bonus in your package..

lower basic pay and higher bonus is quite typically in SMEs... a smart way to hedge operating cost..