5k isn't much these days for a CDN BJ70. The mileage is low too. Not often do 3B's come up for sale with less than 300k and there's upgraded suspension too boot with poly bushings and anti reversible shackles.
Spraying the frame could've had preventative intentions behind it instead of hiding things. This is driven in winter so he was probably trying what he could to defend himself from the salt. If he was hiding it I don think he would've stated there's some frame rust in the email. The timing chain chain does have me a little perplexed however.
If you're a do-it-yourselfer then I don't think this is a bad buy provided the frame and body aren't gone. If you plan on taking this to a mechanic to get an oil change then perhaps a cruiser, or at least a 70 series, isn't for you anyways. One of the perks of these things is they are so darn easy to fix and figure out on your own compared to everything else on the market these days.