Should we ask for a fixed fee or per-unit pricing?

Neither is inherently better; they distribute risk differently. Per-unit pricing tracks your unit count, which matters if the community is still building out. Flat pricing gives you a predictable budget line and removes any incentive to argue about occupied versus total units.

What actually matters more than the model is what sits outside it. A low per-unit rate with meeting attendance, collections, and reserve coordination billed separately can cost more than a higher flat fee that includes them.

Ask every bidder to state each requested service as included, extra with a price, or not offered. Without that, the models are not comparable at all.