this is still an awesome project, unfortunately there will be lots of python and ruby hipsters here who will dismiss this project... it doesn't matter, since most software you use is built in C or C++, and that won't change anytime soon :-)
Things have changed a lot - more tools that allow bozos to get into engineering these days. There are just more wannabe engineers now so the % that is good is just smaller.
major chip manufacturers probably have reference designs you can get, which include some of their parts, and which should be a good starting point.
you will indeed need to have access to advanced PCB fab and assembly subcontractor, but with some digging around you can find those.
the biggest problem is that you'll need hardware and software engineers who really know their job and can do the schematics, layout and firmware - doing a cell phone well is not an easy or small project, certainly not if you want to do something at a serious level and go beyond hobbyist type hacking.
you'll also have to do research on where to get an OS - developing this yourself is a huge project, probably just as big if not bigger than doing the hardware design. I don't know if it's possible, but perhaps you can get android OS source code and use that as a starting point.
you'll have to make each part of the hardware talk to the OS which means writing some driver or glue code, which is a whole other job. I'd try to use standard peripherals/ICs in your design for which android already has drivers.
without knowing more about your project, I can't really help more than this - if you want to talk about it feel free to msg me.
Is it a good idea to buy a used car from a rental company, say entreprise or hertz? What is the best way for someone international to go about buying a car in the bay area?
based on experience I can recommend developing content around your ecommerce business and the problems the products you sell are solving, and using that to bring traffic to your site.
of course you still have to spread your content so for that you have to work on twitter, facebook, ... connect with people and help them spread the word about your content.
I think for YC you can just come on the visa waiver program. You're not going to do any productive work on your startup really, right? all you will do is have meetings and listen to talks?
you can incorporate in the US, and from what I understand, once you have the corp you have more options to apply for visas, such as the H1B, O, E, ... visas .. you will still need a US person to be involved with the corp such that they can sign for you (that is what I've been told).
but the best thing to do here is talk to a lawyer - I'm not a lawyer, and I can't give any legal advice ...
what products are you going to sell? it really depends on the product.
if it is a physical product, just keep proof of sending the order on file such that you can prove to paypal that you've sent the goods.
if it is a digital product I recommend you get a specific service to deliver the product and handle the transaction, such as shareit, clickbank, digital river, ... they know what to do with chargeback for digital products.
I use last.fm for discovering and listening to music.
I also like grooveshark if I want to listen something specific and share tracks on social media.
I don't really organize music because I don't have time for it. But I do have an old iTunes collection that needs organizing and there is no proper tool out there to clean the collection up automatically. I tried tuneup but it doesn't really work well and the software is not very robust or fast.
Regarding creating music - I'd love to see more comments about that here - most of the above comments are about listening to music :-) what about music creation?
Personally i grew up playing the piano but then dropped it after years of suffering and starting using hardware and software for semi-pro music production .. and eventually became a developer of hardware/software for music making :-)