Tell them that you really appreciate them as good renters who take care of the house and you would hate for them to lose part of their security deposit for emergency lawn maintenance and fertilization to get it back to the before Condition after they move out.

Add in a big buffer as there are always surprises.

@Jon Graham Wow I'm surprised at some of the comments here.

Sometimes we have to take care of things during a holiday, be up late at night due to emergencies, give up family time to fix up a place and get it ready to rent out again.If you don't have each other to talk to, to rant and rave with about this or that, that happened that day, then it's a pretty lonely place to be.  

Personally, I was surprised by her reaction, I was expecting a counteroffer.. but.. nothing yet. 

. :)in addition, our houses are in 5 miles radius and i can get to any of them within 20 mins with traffic..you really have to have systems (help) if you are going to take a long vacation. you have to have google voice, an assistant if they have to show the place, a crew/handyman that can access the keys from a lock box and STILL.... it's stressful because it's your property and those people can "flake out" at any point.but you have to train them and you do it by saying "i am going for 3 weeks, you are dealing with everything"... they might surprise you!!

thanks everyone I think I might have to do the cash for keys but now I have to figure out a date to do it and the place is well maintained (surprisingly).

You can get away with a surprising amount of deferred maintenance...

BRRR - I'm surprised no one has pointed out the number one issue with flipping ... taxes.

@Wade Garrett This is actually considered a emergency for liability and security reason.