Write some Software for SEO/Keyword research

I am looking for someone to build an online software tool which will have an API into the likes of Google, Bing, Yahoo etc. to get data for SEO/Keywords research. I want the software to be able to provide keywords for a particular keyword or keywords which have search traffic, with certain aspects to it. There are already products out there like MOZ and others and not sure where they get there research from, but I imagine it is from the search engines. I want it to give similar details for each keyword - so if for example the person searching puts in say "Business" as the keyword - the tool will list all keywords with that term. This list should then provide information like: the search volume; the page authority of top 10 ranked websites for each keyword listed; The Domain Authority for the top 10 website listed for the keyword; The number of results on Google for the term; Amount paid for the search term on Google, Bing etc,. It would be useful to discuss what other data can be gleaned by such software and then show this or not, depending on how useful it is. Please let me know when you reply if you know whether this type of data can be obtained via a free API or if it has to be paid-for. If paid-for then how much. Please make sure you make reference to this in your quote, if not necessarily the costs or amounts, but that you know how this works - this is important as part of your reply. Other functionality would include: - The ability for the user to include related topic keywords or not. - The ability to narrow down the results by: Search volume; Page authority; Domain authority; No. of Google result; Amount paid for CPC on each search engine. - Automatically works with a monthly subscription setup, so that if the user stops paying, they stop having access. - I'd want the software to be automated, so it knows when someone has signed up and paid etc. With an email confirmation setup process too. - The ability to say how many words in the keyword string. The tool will be a paid-for product, so needs to have the relevant access setup linked to a payment source, probably PayPal to begin with. This will be a monthly subscription. It may offer a certain level of free service, perhaps to either limit the information given out on a search, or the number of searches a user can do per day, or even the number of keywords provided per check. Also, some of the functionality may be restricted. It would be best if this was setup so that these could be changed via a panel, so that each option could be tested. I would probably build this into a WordPress website, which I am happy to set up, but will need to work together to build-in. When replying please make reference to Russell. Also, let me have details of other work you have done which is similar to this. I look forward to hearing from you. My budget is around £350 for this project.