Hi Braden, in case this is of interest-use. I've setup Sage for a bunch of my clients over the last ~5+ years on various environments that are similar to what you want to do.  I don't have a howto guide per se, but some basic hints to point you in the right direction?
(a) you can run sage on any cloud/VM/server hosting provider you like-trust. and ideally are comfortable setting up / managing etc.  note the market is full of hosting providers. Sometimes decision of provider to go with will be driven by (1) Familiarity and trust (2) geo-location of data centre - ie if you are in canada maybe you want a provider that has a DataCentre in Canada   (3) possibly there are other factors I won't discuss but there can be many - including personal preference. :-)

(b) ultimately you will need to mimic on the external hosting provider - something similar to what you've got now.  There really is no big change other than the fact your server is hosted - in some remote data centre instead of under the desk in the office. (approx).  So this can mean for example

-- setup account with hosting provider for account management, billing

-- commit to a server rental and pay them money to get rolling. Ideally spec / size up your server requirement based on what you had in the office.  So maybe a modest size office term server/RDS server you are looking at  a single server, 4 cores. 16gb ram, decent amount of disk space (200+gig?) depending on your data needs for your team / based on your current server resource use.

-- get windows server installed. you will need host provider to deal with license, or you need to BYO License / buy license / use for activate-install. You need some windows version that supports RDS/Termserver. Probably to do this in official MS way means a domain controller and linked RDS-TS Roles active on same host.  MS don't recomment this as baseline (They prefer DC on separate host) but it is still doable as an all-in-one server.  Alternately there are non-MS-term-server-solutions for windows that are possible. I won't get into that here. They are basically 3rd party drop-in equivalent and quite doable, not that hard, but not officially MS-sanctioned, but doable and functional for sure.

- make sure you have decent baseline firewall protection in place, possibly protect access to server with VPN, putting RDP-TS directly on public facing internet is somewhat inherently risky. There are 3rd party add-ons possible if you dig that can help protect RDS/Termserver from hacker logins. One such thing is called "RDP Defender" - legacy app bit hard to find now. But it works well.

- make sure you have updates run, and scheduled to run automatically on the server. Or stay on top of your updates.

- make sure you have backups setup, tested, and working. Nothing quite as fun as putting in all this work and losing all your data in 3mo because you forgot about setting up backups.  And-or good to have an option in case an RDP hacker gets in / Malware / crypto and you lose your server that way. Nice to have the option of "Delete server, restore from last night backup, carry on".

- assuming you have those things all good. You basically do a vanilla sage install in the server. Full bundle - server components plus client app. Kind of like a vanilla install on a desktop PC.

- setup a local 'share' folder on the server for sage data to be stored in. Such as C:\sagedata

- setup users in your server/domain environment, set them up for RDS/RDP access

- test access as (user) and make sure can run sage.  RDP in as second concurrent different user, fire up sage, test concurrent use.

- plop your data files in C:\sagedata (for example).  Make sure your license for sage is good for concurrent user mode. Open up data file as USER1. Then in second RDP parallel session open same company file as USER2.  Make sure all goes to plan.

- you are basically good now.  You just need to make sure you backup server regularly, backup data regularly, run updates on server regularly, make sure it does not get hacked, make sure team don't use weak passwords, and ensure people use the server responsibly / suitably.  

You have basically all the risks of a normal server hosting (On-prem) arrangement except you have added risks of (server is in a remote data centre, is more exposed to internet) - and so you must be extra careful to be sure you don't accidentally lose all your data, leak all the data to 3rd parties via "oops weak password on user RDP account ha ha funny" or something like that. 

So all that to say, that you may need someone to help with this work, or maybe you won't depending on your level of technical expertise.  Arguably it is not insanely difficult, so much as there are a bunch of added risks with this kind of config, and it is important you do not over look those and end up having a really bad day a few months down the road after a "happy successful server setup".

Tim