I hope you don't think to make production with a 3.5kW spindle.
Normaly electronic can support 50 and 60 Hz. The main problem is with motor. At 60 Hz, motor run faster and the current drawn by the motor is lower. Lower current = less power. Higher speed on vacuum pump = more power requirement. The motor have a very short life.
Before buying in China, i suggest to you, to considere other cnc builder like AXYZ (cheap), KOMO (top quality/speed) or other company with support in Canada.