What type of developers to hire for outsourced development?

I'm trying to build a minimum viable product SaaS website as a proof of concept, and wanted to know what type of developers I should be looking for if using an outsourcing website like odesk / vworker / elance.

The website is pretty simple: it could be built on an open-source platform like WordPress, but would need to have the functionality to enter information into a database via web browser, and then retrieve and chart the information from the database later on. I would also need to define multiple user types that have different privileges and access to sub-pages on the site.

Should I try to look for an agency that has the capacity to handle the entire project? Or should I look for separate database and wordpress developers?

I'm not worried about the wireframing and design - I'll have that done separately.

I would advise against outsourcing your core business. If you don't know the technical aspects hire or partner up with someone that does. Trying to hire an expert when you don't know much will almost certainly end badly.

I'm not against outsourcing in general but if it's your core business you need to have much more controll than you can get with contractors

Considering that the DB and the site are pretty tightly coupled, I think it might get pretty convoluted if you hire separate developers, since you'd have to do a lot of coordination and micro-management.

I'd suggest that you hire a WordPress developer/agency who knows database, give them work incrementally, and don't hesitate to switch if the job isn't being done properly and timely.

The downside with hiring one developer/agency for the whole website is that they often end up making compromises in the APIs of one part of the project to support some feature, so things don't remain modular. Having two different agencies would ensure that you get a more service oriented architecture which would be easier to maintain.

Being a vendor in outsource domain, I would suggest, if you wish to outsource, outsource both the database and web development to a single agency. That will be much easier for you to manage and also much easier for the vendor to develop.

For incremental outsourcing, I would suggest setting milestone on your project (this can be done in Elance, I am not sure about others).

I have seen many companies, selecting upto two agency for the initial phase and then making a final choice on the basis of their performance. It all depends on the complexities of the business.