Is there such thing as having too many links on your site? I am talking about a sidebar section labeled 'resources' or something. If I then had 5,10,20+ links to different websites but they were all for similar products/services such as web hosting or SEO for example could this be detrimental for my site? Would Google punish for this? None of these links are spammy and all use appropriate anchor texts.
Also if I put up links for a client on say 30 sites all on the same day linking to the same url but with different anchor texts is it also possible that this will cause problems?
The short answer to both your questions is yes. Keep your link juice spread to a minimal amount of external sites is best for you and your customers. Not that link buying is favourable in the first place.
You should look to spread building your links throughout several days, if not weeks. Look for quality rather than quantity and you will hit the mark.
Suggest reading up on link bait as a viable alternative