We are buying a house and the neibors have there fence 10 feet onto our property.

First of all, you should resolve this issue before you buy the property.  Otherwise, you may end up having boundary disputes with your neighbors after you move in and it is probably not going to be a pleasant experience.   Under RCW 64.06.020, the seller needs to disclose whether there has been a boundary dispute over this property and whether a boundary survey has been done. So, you want to first check the seller's disclosure form. If your seller answered "no or don't know" in those questions.  You could first ask your real estate agent to get the property's boundary survey and title report.  This way, you can confirm whether the neighbor has right to put his/her fence on your property.  If you are convinced that there is a problem, you should inform the seller about this issue and request him/her to amend the disclosure form.  If the seller refuses to amend or deliberately conceals the fact that there have been problems relating to this, then, then you may have claims against the seller and you may be able to rescind the buy-sell agreement before closing.  The house is going to be your property and you as the buyer needs to exercise due diligence before closing.