Typically heirs who put a property on the market just want to be cashed out. If there are even just a handful of them getting decisions made without causing squabbles is a real threat and it's one most want to avoid. Especially if they're spread around the country (or the world) the logistics alone can be enough to make them want to sell.
If the NI you listed is the actual Net Operating Income (NOI), their ask is a 6.2% cap which may or may not be a little rich in your market. If you are confident you can get market rents, some utility costs moved to the tenants and some Other Income in the form of paid parking there's some nice upside though. Also the extra land may have some additional value, especially if it can be built on (or expanded onto by the existing building).
Once you're sure you've got a handle on what your expenses should be the other thing to look very closely at are the deferred maintenance and any building systems that are reaching the end of their life (roof, boiler, paving, etc). I would hire an engineer to assess what these are with cost estimates/bids. This will cost more than an inspection from a home inspector but there's a lot riding on it and will be money well spent.
If you are confident of the upside, why not offer the heirs their full asking price subject to them making all the repairs and replacements identified by your engineer, with the fallback that you're willing to have the work done yourself if they will reduce the price by the cost of the work?
If you can get the market rents, some other income and keep the expenses to 28k your effective cap rate is in the 9% range which is pretty nice.
One other thing to have checked out by a pro is the commercial lease, they're a whole different ball of wax and each is typically one of a kind in its terms. It's important to know how long the tenant will be there on lease and what can/will happen at expiration.
Good hunting-