Sponsor unit - allowances for upgrades/renovation

Hi Streeteasy members! I wondered if anyone has experienced the process of purchasing a sponsor unit and negotiating an allowance for choosing renovation materials (i.e. changing cabinetry, bathroom fixtures, flooring, etc.). Is that a common process? Also, can you include a rider in the contract that stipulates that the quality of the renovation (completed by the sponsor) is of high quality? I am looking at sponsor units in Brooklyn and all of the renovations are being done by the sponsor, so I want to make sure that they are using nice, quality materials instead of hollowed out doors and shoddy flooring. Thanks for your comments!