If your website homepage have min 15 external/outbound links... then your site is quality website in eyes of Google. If homepage have more then 40 links .. then website will be Average website.. and less worthless.. If website have more then 70 links on single page .. its looking like a spam in eyes of Google..
No one truly knows the answer to that question. The idea is to deep link, don't get too many too fast and get links consistently.