But as her taxi disappeared round the corner I thought, hang on a minute, maybe she's not joking.
I thought some more. My neighbour seemed to know very little about the couple moving into her house.
They responded to her vacancy on Gumtree, saying that they were moving to London from overseas and needed a house to rent for six months. She agreed to let them have her place in return for all the rent upfront.
I read somewhere on the internet that buy-to-let properties were being targeted by gangs of criminals looking for houses to use as cannabis farms. They tend to rent houses in the suburbs (like ours), where they rip up the floorboards, knock down walls and tamper with the electricity and water supplies to provide the perfect environment to cultivate the plants.
One insurer said claims from landlords for damage to properties that had been used to grow cannabis rose 30 per cent last year.
Momentarily I was convinced my neighbour's home was going to be turned into a greenhouse to grow drugs.
On one website, I found a list of warning signs that landlords should look out for. At the top of the list it said "beware of tenants who pay all the rent in advance, in cash". Uh-oh.
Be suspicious, it said, of tenants who show an unusual interest in the electricity supply. One of the very few things my neighbour had mentioned about her tenants was that they insisted the rent include the energy bills.
Tenants who want to move in quickly should also set alarm bells ringing. Don't offer short-term lets, it said. Oh heck.
Point five. Don't be fooled by a "front couple". How had my neighbour described her tenants? "A man and wife, middle-aged, seem really nice."
I resolved to keep a very close eye on her house and if there was so much as a whiff of anything suspicious, I'd be on the phone to the police.
Call me paranoid, but then I started to worry about what was going on in my rental flat. It was ages since I'd inspected the place and I remembered that the tenant did say he enjoyed gardening.
I decided it was a good idea for me to swing by the place, you know, just in case.
I emailed the tenant to tell him I was going to pop round "to make sure everything's okay" and drove over the next day after he'd left for work.
It's odd, snooping round your own flat when someone else lives there. I tiptoed (why?) from room to room. I even knocked before I went into the bedroom, though I knew there was no one home. Everything looked fine until I went into the kitchen and spotted half a dozen plant pots on the window sill. I scooted over for a closer look, but they weren't cannabis plants, unless the tenant was growing brown sticks.
Wrappers strewn across the kitchen worktop told me someone has got a serious chocolate addiction, but there was no sign of anything else unusual.
When my neighbour's tenants arrived I was hugely relieved to see there was nothing odd-looking about them, either. They weren't carrying bags of fertiliser or a suspiciously large quantity of lamps, no plant pots tucked under their arms. Like she said, they seemed like a really nice couple.
Mother-of-two Victoria Whitlock lets three properties in south London.