Do you know what the seller meant by "sprayed"? As in sprayed with water to keep the undercarriage clean or sprayed with some type of undercarriage coating? If sprayed with water during regular washes, great, nothing will be covered up & you will be able to see a nice clean frame in most cases but if it was sprayed with paint or a coating, it will make it a little more difficult to determine the actual condition of it since potential signs of deterioration will have been covered.
Have you had a chance to inspect it yourself? If it is not within a reasonable driving distance, you may want to hire a reputable mobile auto inspector to look things over...that can cost around $150+ but not a bad idea to get an outsiders objective opinion that has had the opportunity to physically look things over so that your "want" doesnt cloud your judgement. Typically, a mobile inspector will call you after going over the vehicle & discuss their "checklist" with you and email you a copy of it.
I wouldn't put too much value in what the seller is telling you unless there is some type of documentation or a way to verify it upon a physical inspection. That's not to say his claims aren't true...such as the 50yo woman original owner that drove it to work...but if there isn't a way to verify it, I wouldn't let that weigh too heavily in your decision making. If you haven't already, pull a carfax or autocheck or both to get an idea of the history. Again, wouldn't let either one of those influence your decision too much but it will at least help uncover any potential inconsistencies in the history.