And yet it is not so simple. If I want a friend to live with me, financial shrewdness goes out of the window. At market price, the flat’s second bedroom, with its view of the garden and en suite bath and shower, would cost about £170 a week. But at that price none of my friends, most of whom are in their first jobs in the media or PR, would come near the place. So, to lure a friend, the room would have to cost £120 a week.

Altruistic though I am, I am acutely aware of what a good deal this is. I have spent the past few years renting the sort of property in London where having both functional heating and hot water is too much to ask; sometimes I have paid more than £120 a week, before bills, for the privilege. Then there is the soul-crushing passage through the hands of the unhelpful, inefficient and often unpleasant estate agents that deal in cheap rentals. My tenant would bypass that entirely. So I want whoever it is to be worthy — possibly even the perfect flatmate.

So what am I looking for? Intimacy is not necessarily it. If you have a great time boozing with your most hilarious pal, and tell her everything, why sully this with quibbles about washing up and council tax? Yet friends may be intimate and well-suited tenants at the same time.They are the practical sorts who don’t court drama and regular emotional upheaval. They have a steady job and a boyfriend or girlfriend who takes them out most nights. (The flipside is that the boyfriend/girlfriend will no doubt decorate your sofa from time to time, and possibly even voice an opinion about what to watch on TV.) With such a tenant, a frank word about taking out the rubbish, when it is spilling over the top of the bin and you haven’t been home to fill it, would be received easily and responsively. After all, the property belongs to you, not to a remote landlord, and requires that bit more care.

Every person I count as a friend is reasonable, and undoubtedly most would be fine, if not great, to live with. So what could go wrong? After all, no friend would refuse to pay rent and his or her share of the bills. Nobody really smokes. Nobody would try to foist a cat on me (I am allergic to the devilish creatures) and everybody knows you have to wash up. Since the second bedroom has its own bathroom, the tenant can tuck him or herself away. Shampoo choices, loo paper buying and bin-emptying regularity will be out of sight and out of mind. Should my flatmate wish to host a guest privately I will not have to bump into him or her as we both head for the bathroom. Normally, I would insist on sharing with a girl, but the en suite bathroom means that sharing with a male might not be the grimy experience of legend.

The only real cause for concern, then, is what happens in the shared space. The big plus to renting the second room to a friend, rather than a stranger, is that it is a comfort and a joy to find them on the sofa when you come in, or to hear them at the door when you are sitting there alone in your room. But it is less joyous to come home tired, wanting to relax in front of the TV, only to find a noisy gaggle of your tenant’s friends commandeering the sofas. Mostly, my friends’ friends are my friends and the sight of them would be welcome and uplifting. But there are always a few stragglers with worrying penchants for DVD marathons, noisy fry-ups and foul takeaways. This sort of intrusion would be disheartening: my long-awaited dream of an elegant oasis in ruins.

For all that, I should not be smug. There is the very real chance that just because I want to live with somebody, he or she will not want to live with me. In fact, the first person I asked was already committed to living with other friends. Another one actually has a cat — and needs to find a home for it first. Two are moving in with boyfriends. And September is far away — nobody knows what they will be doing then. It could be that, far from being spoilt for choice, I have to use less personal ways of finding a tenant. I may have to post the room on an office noticeboard, send a group e-mail, or advertise online. Still, I can charge a stranger the market price, thus paying off my mortgage more quickly.

Perhaps a solvent stranger wouldn’t be so bad. I still get to make the rules, after all . . .

FACTFILE

Where to advertise for a flatmate if none of your friends fits the bill:

www.gumtree.com: a trusted favourite, nothing fancy about it, very easy to post a free ad.

www.flatmateclick.co.uk: very clear — you register to post an ad, but it’s free.

www.loot.com: first port of call for most people trying to rent in London, Manchester and Liverpool. You can place your ad online (£11 a week) or in the publication of that name (£10 a week). Telephone numbers vary for local editions.

At work: try an office noticeboard or intranet listing.

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