Generally speaking - no.
Most of the low-end websites you encounter on Flippa are nothing but templates (where the seller creates the same site over and over again and sells "copies" of it). If you want to buy a website then first make sure that a) it's generating revenue; b) it is indeed the website that is generating revenue, rather than the current owner of the website (who would start generating revenue for their new project, rather than the website you're buying, immediately after you take over).
But if a template-site is actually what you're after then why spend the cash on it? With the information you have here on BHW it will take you an hour or two to put together an "SEO Service" site that is as good as the ones that are being sold on Flippa. You need to bear in mind though that to provide SEO service you would actually need to know about SEO (unless you're reselling), as well as have a strategy for finding clients.
In any case, only buy sites that are already generating revenue and don't believe any of the "this site has massive potential" stories, no matter how good they sound.