It depends on the quality of the backlinks. There is no hard & fast rule about how many backlinks you can create a day, as long as those links are created in a safe manner, which means that as per Google's algorithms & Google’s Webmaster guidelines, you’re not participating in "link schemes".
Google’s Webmaster guidelines clearly states that using "link schemes" like paid links, cloaking, doorway pages, hidden links, etc as a way to create more links per day to manipulate PageRank is a violation of its terms of service.
Ideally, always get high PR (PageRank) backlinks between PR7 to PR10, as these are the safest backlinks to get without any worries about a penalty because high PR sites have demonstrated trust and authority online, as per Google algorithms.
About backlinks, remember that it's all about quality, not quantity.