thanks for the request. The database size depends on a lot of factors, but can fill up a SQL Express version soon.
Over time we move out older collected stuff, so that the database will stabilize and will not grow that much.
There is a calculator for all this:https://www.veeam.com/kb2246
For a test you can maybe use a 90/180 day MS SQL Server trial if you do not have a SQL license. https://www.microsoft.com/en-us/evalcen ... r-2014-sp2
Usually you can install the trial version over the existing SQL Server, so that you do not have to change anything.