Selling property - looking for creative deal/finance suggestions

[Bob Smith]

Selling a single tenant commercial property to the tenant.  The property is rented for $4k a month (with tenant responsible for all repairs/maintenance but I pay taxes/insurance), on a long term month to month deal, and the tenant has offered $725k.    Could easily raise the rent to $4,500 as it would be a good deal for tenant compared to his options and haven't raised the rent in about 5 years.

In my mind it's worth about $850-950k (or worth that much to me) as it is a half a block past where current redevelopment efforts are. So it's just a matter of time before walking traffic will continue past this property. Plus, it has a large parcel next door that somebody could buy both and combine for a better use (like a small hotel).

The property is paid off.

One thought is to take his $725k since he can qualify for a loan at that amount but make the sale price $825k with a $100k low interest second.

Anybody have any other thoughts to try and bridge the gap?