There is no clear easy answer on... How many Facebook.com likes does a business need?
First things first are you trying to improve your position on search engine rankings like Google.com ?
In this case it may be better to have it constantly and slowly growing. Just like Google likes to see updates on a site in order for it to rank well. Then it would make sense for the same to work via your Facebook
business page. However you need to have the Facebook social plugin on your actual website in order for it to fully help.
Click here to see how to get the Facebook.com Social Media Plugin.
Do you want to look good so people assume you are a legit company and or have a good honest running business?
Well there is no perfect answer for that so I will try to break it down.
Look at your competitors first and of course you need more than them. By more I mean enough more for you to be the clear choice. If your competitors Facebook.com Likes are 1,000 for example then you need 1,500 at least. More would be even better.
Small Local business seeking customers just in their surrounding area : around 300 likes or more than your competitor.
Small business seeking customers from any market area : 1,500 likes or more than your competitors
Large business looking to find new customers via Social Media : 10,000 likes
The likes are not the only thing that matters. Having your page actually being used is a major part of looking like a well liked business. You can not make customers care enough to comment or share your Facebook post even if you are the best business ever. You can buy likes for any post on your business page. In order to have something for people to like you need constantly post. Don't have time for that get yourself a GHOST WRITER!