One of our tenants is moving to another of our houses so the wife just bought a new stainless steel range, one of our other tenants cooks in grease 24x7, she got $100 range from Goodwill.

Tell them you won't be raising rent at this time (this is what tenants most fear at change of ownership); that will put them at ease and demonstrate good will.

You could even do something for them from their "want" list to improve their place and gain their good will. 

Of course, if it is not habitable because of landlord negligence, that's a different story.If a unit floods because the sewer main collapsed unexpectedly, the landlord most likely bears no responsibility and -- according to contract -- is not responsible for motel room bills.I have seen a landlord being forced by the city to put tenants in hotel rooms -- 1 week for adults and 2 weeks for adults with kids, because the city red-tagged several buildings.Now, what you are legally obligated to do, and what you may end up doing for good-will reasons, that's not the same.No legal advice given.

Now if they pay even more when they stay, now that could improve NOI, but I don't see it happening ...Rochelle:Steve is even more cynical than I at times ;-)   If you simply set aside a piece of the property and allow the tenants to garden there, there is no real cost to you and the goodwill could keep tenants longer term.An alternative is to see if there is a urban gardening business/co-op/organisation in your area who would {preferably} rent the plot from you (auxiliary income) or come in and work it for free (an organisation) ... with either approach you could make involvement of your tenants who wish to garden a condition of any arrangement.This may be a nice perk for 10% of your tenants, but do not let it distract you from the main job to get done.

You have grounds to say no but retain good will for trying to work with her.

BTW, I've done some neighborhood good will with dumpsters when they aren't full, great opportunity for neighbors to clean stuff up offering free trash removal.

Community garden to foster goodwill for the rental properties you own in the neighborhood?

I'd say they have already used up their good will and it is time to move on to the next step.  

If a tenant agrees to a new lease under different terms, that is strictly at the good will of the tenant.Your best bet, in my opinion, is to maintain the current leases already in place and make any changes when those leases expire.