The reason that Google beat Yahoo was the fact that they used a scripting language(Python) which ensured a short software cycle and they were able to come up with updates and new products very fast while Yahoo! with C++ took some time to catch up and by that time, Google had launched something new. In short what I'm saying, Use a scripting language e.g PHP or Python.
This will cost you a lot of cash also because of the API/ Widgets if you want it done professionally with Security taken care of. Web Development companies will charge you upwards of $25,000 while you may get a group of freelance coder, designer and Front-end programmer who may do it for a total of about $10,000. This is an intensive project.
You may also check out the Scripts available all over the internet. They are affordable because they are sold to masses. But for what you want - something custom - it will cost ya.