There is no limit on the amount of hubs to post on HP.
Before you hire writers you should heed the warning of Relache and read the FAQs first. However, you can hire content writers to write for you. Bear in mind that this is not a blog and so your writers should create articles that are informative, well researched and interesting to read.
Absolutely no copied content so before you post them, use Copyscape to check for plagiarism, it's free to use. I have had clients tell me that other writers have copied content and sold to them so just be careful about who you hire. Check the articles before you pay for them so you are not robbed.