Could you advise what kind of server environment you have right now? Do you have an existing vCenter and ESXi hosts? This is a requirement for Horizon View. If you do, do you have the capacity for the 20 VM's? May need an extra host if you're close to contention as it sits today. VMware offers a free version of their Consultants tool called Lakeside Systrack. It is a capacity planner for View installs. You can try it out in your environment by going to Horizon Virtualization Assessment | VMware If you don't have a vCenter, then that is a pretty hefty expense to add. You may want to look into the Horizon Air hosted solution. Costing for that solution can be found here: Buy Cloud-Hosted Desktops: Horizon Air Desktops & Apps | United States
Let's assume you have vCenter, and are ready to deploy Horizon:
If your boss wants redundancy you will need the following components:
Horizon View Composer Server (Server 2012) (Composer can be installed on your existing vCenter Server if you use a Windows vCenter, not VCSA)
Horizon View Connection Server Primary (Server 2012)
Horizon View Connection Server Replica (Server 2012)
Horizon View Database Server (Server 2012) (Databases can be put on your existing SQL server if you are using external SQL for vCenter)
Horizon View Composer and Event Database (Free SQL Express can be used for an installation this small. If you ever grow up, you can move the database to a full SQL instance)
You don't have to have a load balancer, per se. You can simply have your 2 connection servers (standard and replica), and if 1 goes down just point users to the other. The optimal configuration, though, is load balancing.
Will you want external access from the internet? You can deploy the Horizon Access Point which is an included Linux appliance. That will save you the cost of another Windows license you'd use on Security Server. The Access Point appliance is also designed to be load balanced in an HA pair for redundancy.
I hope this info helped. Please feel free to ask if you have any more questions, or follow ups!