How to double WAN speed with 2 WAN connection?

I assume you are trying to increase your downloading speeds by combining both your internet connection and possibly a neighbors via unprotected wireless. Load balancing will allow more users/applications to have higher speeds but it will not combine the speeds of both lines. If you have two 1mb connections you will not get a 2mb connection by load balancing them, you will allow two users/applications to run at 1mb simultaneously.