1.Check the Marketplace
There are many marketplaces to choose from when buying a website, some of these venues are fantastic, some are less so. You need to be certain the venue you are looking at and considering buying a website through is trustworthy and established. Check the number of listings posted and make sure there is enough activity to be sure that the venue is a good place to be thinking about purchasing websites for sale.

2.Investigate the Alexa Rank
OK, so what is the Alexa rank? Well its a ranking of a websites popularity and level of usage, its by no means a perfect measure by which to judge a websites success, but it is a good way to tell if a site has been around for at least a few months. To check a site just visit the Alexa website and enter the URL of the website you are thinking of buying, if it says it has no information on the website and you have been told the site is over 6 months old, then beware.

3.Check the WHOIS
Every domain has its owners records kept, and you can find out who has registered a particular domain by searching the WHOIS registry. Many sites offer WHOIS searchs free of charge, a quick search in Google will turn up a handful for you, choose one and then enter the domain name for the website you want to buy, if the information returned doesnt match the information you expect to receive with regards to the seller, then beware.

4.Check the Website is listed in Search Engines
If the website you want to buy is fairly old, and its claimed to be getting traffic from search engines, then you can check within the search engines to make certain the site is actually indexed and therefore capable of driving search engine traffic to the website. To check a website is indexed in Google, go to Google and type in: "site:www.DOMAINNAME.com", without the quotes, you should see lots of pages, and a number telling you the number of pages Google has listed for the site, if the number of pages is massively lower then the number you would expect given the overall size of the website you want to buy, or there are no pages at all, then tread carefully.

5.Confirm Proof of Revenue
A lot of websites you want to buy will be earning some revenue, meaning the seller is claiming the website is making some money. It is essential that you check proof of any revenue claimed by the seller, often they will advertise a website as being with revenue, when in fact they mean it is potential revenue, and sometimes they will simply lie to try and make a sale. Revenue can come via various channels, PayPal is the most obvious form of taking payments for many websites, but it maybe credit cards or some other payment method, whichever it is, make sure you check the revenue does exisit.

The above points should set you on the path to checking the website for sale that you are thinking of buying isn't a scam, make sure though that you check out other important items to look out for and fully convince yourself that the website in question is worth buying.