Building an elite server for offsite storage & VMware- potential for paid consulting work!

Hey all, this is my first post on this site and I'd like to start by expressing my gratitude for this forum. I've used it as a resource for years and am happy to be joining this community with the intention of assisting other members in the future. I own an IT service & consulting business in OK and primarily service commercial clients. I have several employees and feel fortunate to be able to say that my business has grown rapidly over the past year. So... the issue at hand:

I have numerous clients that are either currently using or are very interested in offsite backup services as well as utilizing RDP (remote desktop protocol) on Windows based workstations to access applications & data stored on a secure, high end server elsewhere. For the past year or so I have been working with a large national company that offers managed services and simply referring this type of business to them. I recently made up my mind to stop doing this and invest in the technology I need to begin offering my own managed services products. While obviously money is a factor, I am prepared to make a substantial investment for my business and plan on doing this right.

SO, I am very interested to hear ideas on the best ways to do this. I will almost surely be building this first system in house and I'm just not sure which route to take. Keep in mind that for now I'm wanting to build a high end server that has both redundant storage (10-20TB probably) AND other various high performance components that will be the muscle driving the VMWare I use to host client applications/data.

While the virtualization side is certainly going to grow, this server will probably be used mainly for offsite backup/storage for client data in the beginning. I'm open to any and all expert advice & discussion and have listed a few questions below that may be easier to answer directly:

1) What operating system do you think would be ideal for this server? (Server 2012?)

2) What is the best/smoothest process for syncing client data on a scheduled basis (night, weekly, etc)? FTP? Software that makes it simple to do?

3) What type of hardware do you feel would provide the most cost effective solution? Motherboard, CPU, RAM, RAID, GPU, PSU, cooling, etc.

4) As far as the VMware concerned, has anyone had success with a certain software platform that is both powerful & somewhat simple to use (for IT professionals)? The primary applications that my clients will be wanting to access on these servers are business related programs like QuickBooks, MS Office and various proprietary software designed for specific fields.

5) What kind of budget do you feel would be reasonable for something like this? Remember that I'm NOT building a data center or server farm; I'm just wanting to build a solid system that will be configured to automatically securely store offsite backups and will also have the power to run VMware. I will certainly be growing this into a server farm eventually but for now I'm just getting started.

I apologize for the length of this post and really hope it doesn't dissuade people from chiming in. I want to let you know that if someone recommends a route for me that I'm very impressed with and agrees to provide guidance throughout the process of building & configuring this system, I will be offering compensation for their time. In fact, it's extremely likely that I will be giving some money to the users that provide the best insight.

I am ALWAYS looking for good help and can absolutely work with someone from anywhere in the United States so I am not exaggerating when I say that this is worth the time for the right person. I employ several consultants that work exclusively from their home or own office in another state and they couldn't be happier with the arrangement.

THANK YOU ALL IN ADVANCE! I'm looking forward to this discussion.