22 is possible without help. For example,
https://www.warzone.com/MultiPlayer?GameID=19731832I searched an old ladder download, (almost 2 years out of date...), and it featured 19 games with 22 income at the start of turn 5.
For the first ten turns I computed what the highest number of armies deployed is after said number of turns. Here is the result:
1 : 9
2 : 13
3 : 18
4 : 27
5 : 32
6 : 37
7 : 46
8 : 55
9 : 58
10 : 59
Due to reinforcement cards, the numbers are all likely more than the actual income from turn 4 and onward. Also, this data says nothing about a theoretical maximums.
For example, a 5 bonus can be taken on turn 1 with 1 helpful tap from your opponent and China can be taken te taken as first turn bonus:
With some help, you even have an army left to spare. I doubt that 12 first turn is possible.
Edited 9/19/2021 17:09:30