New to Servers-need RDS help

[tek9]

Hi all.
As per the title, I'm new to Windows Server and need some info on RDS. Have a client that just wants a server for basic file sharing duties and to allow 2 other remote users to login and use QB and some other tax programs on the server.
He's replacing an older server (home-built, I believe) with this one. He'll be using it in his office, he's the only one there. And he has two remote workers that need to login to the server to run some applications. I ordered an HP ML350 server with Windows Server 2012 R2 Standard. Questions as follows:
1. As far as I know, you can have 2 remote sessions to the server before requiring any RDS CALs. Is that correct? Does that mean that one user can be using the server directly (I know it's not best practice, but it's a long story with this guy) while the remote people can login with different credentials at the same time?
2. Do I need to set him up with a DC and AD and all that to be able to use the server in this way? Or can I set up some local accounts and have them login with those? (remember he's the only one in the local office, and has two remote users. No more)
3. Is is possible to decommission the older server (I think it's running the same version of Windows Server) and use whatever RDS CALs were installed on that one for the new one?
4. I was considering setting him up with an Edgerouter Pro with OpenVPN and running the RDP through that for security reasons. Is there a better way, maybe built in to Windows Server?

This is my first foray into the Windows Server space, and these questions were probably covered somewhere. Googling gave me alot of differing opinions, so I hope I can get some clarification here.
Thanks in advance.

 

[YeOldeStonecat]

What operating system is his current server?
You can have 2x remotes for Administration of the server. Not really designed for "users". Should have a separate login for each user.
Since this sounds like accounting, yeah I'd want to see active directory. Thus..a DC. BUT...don't use a DC for a terminal server. Virtualize it, Server 2012 Std license allows a local Hyper-V install, and then license for 2x guest servers. A little DC and storage the apps, and then have a little RDS (remote desktop..new term for terminal server) server. Just punch port 443 open on the firewall and setup TSGateway role, much more secure than just doing RDP to port 3389, and no clunkiness of VPN.

Quick side note..."what other apps"? Some accounting apps run on SQL, may get squalks about SQL on a DC....it's not recommended (full SQL that is)...but you can do it.

Kind of a tough situation for just 1x guy here..if he's a 1x man office. I'd almost say just get a couple of extra workstations and have 1x for each to remote into. Certainly a heck of a lot cheaper.
Of spin up a virtual cloud office up in Azure and have them all remote in.