Learn Hardcore Finnish: Kysyn isännöitsijältä huomenna, milloin vesikatko alkaa. - I will ask the property manager tomorrow when the water outage starts.

Because -lta / -ltä is the ablative case, which often means from (someone/something). With verbs like kysyä (to ask), Finnish typically marks the person you ask as a “source”:

kysyn isännöitsijältä = I ask (it) from the building manager
Base word: isännöitsijä
Add ablative ending (front-vowel version because of ä): -ltä → isännöitsijältä

Why not Kysyn isännöitsijää huomenna...?

kysyä doesn’t usually take the person as a direct object in the way English does. Instead:

kysyä joltakulta = ask from someone (ablative: -lta/-ltä)
what you ask can be:
- kysyä jotakin (a noun phrase) or
- an embedded clause (like milloin vesikatko alkaa)

So isännöitsijältä is the normal, natural choice here.

Why is Kysyn in the present tense if it refers to the future?

Finnish commonly uses the present tense for planned future actions when a time word makes the future clear:

Kysyn ... huomenna = literally I ask ... tomorrow, meaning Finnish doesn’t have a separate dedicated future tense like English does.