In Swan's Practical English Usage section 265 on (if only) item (b) would + infinitive (without to) to talk about the future, he gives the following example:
If only it would stop raining, we could go out
I was wondering if we could use (would) in the main clause too. I googled up but all the pages I have seen aren't any different than Swan's. Here's an example I made it up:
If only he would sell me his car this week, I would give him $1000 more.