I'm probably going to surprise ye all, but I don't concentrate on multiples at all. I sit with clients and work out their repayment capacity along the following lines ...
Net salary less mortage repayment (and I'd usually stress test by 2% unless the customer was opting to fix for five years). That would show us (customer and I) what they had left to live on for the rest of the month, roughly what I'd be keeping an eye on would be, for a single person, something in the order of E1,200 to E1,500 a month (after mortgage repayment), and for a couple something in the order of E2,000 to E3,000, depending on kids (if any), lifestyle etc.
The above isn't probably worded that well, but take for example, two married couples both earning E50,000, there's a material difference between couple one who have say E20k saved and couple two, who have no savings, maxed out credit cards and two personal loans - their respective mortgage repayment capacity is very different, it's the main resaon I've always stayed away from multiples, apart as a double check at the end of the process to ensure that we weren't coming up with a crazy answer. I've always found this approach makes it more 'personal' to the customer, as it lets them work our what they can acutually afford in repayments rather than just concnentrating on the lump sum borrowed.
It's a longer process at the outset, but I always believe worth it in the long run (for both parties) ...
Hope that's of some help.
Regards,
BM
P.S. - for those of ye wanting to know what the multiple works out at it's usually around the 3 to 3.5 mark - higher income earners can go to a figure of 4 and sometimes a bit higher. If I ever hit 5, I'd be re-checking my figures!