5LPA to 15LPA in one year. What's the catch? Need thoughts

My brother was at 5LPA in a creative agency between 2022 to 2024. He then moved to Bangalore for a year of PGDP and now got an offer of 15LPA from startup in Delhi.

It sounds too good to be true and doesn't feel legit. The offer letter does not mention working hours or leave policy. it doesn't even have a founder's signature to know if this is legit.

Seeking perspectives on how to approach this and whether if my brother should take this offer and move to gurgaon from bangalore.