DID internet number

I need advice/configuration on which application is needed to receive phonecalls thru internet. There are many applications and services out there but i don't know which one to choose. I will be receiving it by sitting behind my computer (usb-headset etc) - I expect you to tell me where to buy a DID number. I prefer the 88xx variant - It would be great if i could register my conversations and save them on the computer (i guess there are separate apps for this) - Also i need to know how i can receive faxes by having my own DID number. Meaning i don't want to pay for a received fax due to spamming etc(like those e-fax services). Ready to pay for sending faxes. (if this is not possible feel free to comment) I am a small startup and need to have this somehow to control my costs. I have read a lot on this topic and i believe there are some people who know exactly how this works. So please contact me with concrete propositions on how to help me out of this. If you have questions, please submit by PM.