Magic Money

I received an email from my mortgage broker and she says I can get a loan for an additional $10,000. Like magic, I have more money in my house offering pocket! This is of course good news, but it also brings me up to the max I'm willing to make for a mortgage payment monthly unless I get a raise (and non-profit raises won't raise the amount I could pay by much).

I wonder on some of the past houses I've made an offer on if I could have gotten them if put an additional $10,000 to my offer. I'm not sure if it would have made a difference. I've made some really good offers but they can't beat an all cash offer from a flush investor. I keep hoping that the investors will get all the properties they want and there will be room for me and some other first time buyers to get a piece of the pie.

How much is enough to beat out an all cash offer? I've seen other buyers ask the same question and I wish I could know. If there is an equation the banks use to weigh the risk of a mortgage against the higher cost I'd really be interested to see it.