Creating an index using transactional data

I have a dataset of a series of leases.

Variables we have: precinct, date (in quarters), lettable area, price as well as a few others.

These assets are not homogenous, although are comparable.

In some periods, the data is quite dense, where we have multiple entries for each precinct-date combination, at other times, we can go a couple of quarters without an entry.

I am trying to derive a market price based on these leases. Fue to the sparseness of data, looking at period-on-period changes like a typical index won’t work.

What would be a good approach to deriving that market price?