Most lenders require a 620 or better middle credit score for a VA mortgage.
Please ignore most of Trevor's "advice" as it will not help you increase your scores in the short term.
When dealing with collection accounts, it's important to look at when the account was last reported. The older it is the less affect it has on your scores. This is why you do not want to follow Trevor's advice. If the collection account is 2 or 3 years old and you pay it off, when the collection agency re-reports the account to show it now has a zero balance, your score will go down.
Here's a blog I wrote here on Trulia about credit repair.
You need to work with a mortgage professional who will review your credit report and give you an outline of what you need to do to get your scores up.
Please feel free to contact me for more information or help. You can also find info on my VA Mortgage website by clicking the link below.
Senior Mortgage Banker