Maaser on income is based on Bereishis 28:22
וְכֹל אֲשֶׁר תִּתֶּן לִי עַשֵּׂר אֲעַשְּׂרֶנּוּ לָךְ
And everything that You give me, I will surely tithe [lit. take a tenth] to You.
This implies that one should/must give a tenth of one's income, regardless of whether it was earned through agriculture or not.
However, there is no verse stating or implying that one should give Terumah on non-agricultural earnings.