I have three domains that are similar, so I wrote a script to have each of them pull contents from a single hosting account. Each domain has its unique domain name, title and keywors, but all the contents are the same in all three domains. What problems or issues will I most likely face?
You risk being banned or penalized by the search engines. This is the exact kind of duplicate content that search engines do not want. You need unique content on each site.
What benefit do you see by having 3 sites all pulling content from the same database? This is surely going to get at least 2, if not all 3 sites penalized by google.
Straight from Google's mouth: What is duplicate content? Duplicate content generally refers to substantive blocks of content within or across domains that either completely match other content or are appreciably similar. Most of the time when we see this, it's unintentional or at least not malicious in origin: forums that generate both regular and stripped-down mobile-targeted pages, store items shown (and -- worse yet -- linked) via multiple distinct URLs, and so on. In some cases, content is duplicated across domains in an attempt to manipulate search engine rankings or garner more traffic via popular or long-tail queries. Zeek
You are just asking for trouble. Search Engines hate duplicate content like this, I would remove the content from two of the websites and just go with which ever one you like the most. You should check your Google webmaster tools to make sure you don't have any warnings. At first you will receive penalties but that's just a warning shot, eventually you will be removed from Google's index completely. imagine this: What if your job was to find and read the best articles in the world and rank them, and every day you read from a stack of 100 articles. And every day you read the exact same article three times. How long would you keep reading these articles, before you just tossed two of them in the trash, and replaced them with two brand new articles?
This will be considered "Duplicate Content" and Google will penalize you by taking 2 of the sites to a PR0 and the other to a PR1. This will kill any linking concepts you are planning. Then, they will apply a "90 position filter", that will put any SEOed content on page 10 or greater. And finally, they will see that you have the sites on the same host and apply a "SubNet CrossLinking Filter" that should just about make what you are doing, worthless. I've been in this industry for ~7 years and we stopped doing that 7 years ago. Don't you read... The SEs killed this concept years ago.