Maintenance / Capex for lower income large apartment from 1960

[Ben Mizes]

My partner and I are looking at a 128 unit complex that's made up of 8 16 unit buildings, with a average rent of $450. 

The building was made in 1960.

We're not entirely sure how much we should project for maintenance / capex every month, in order to make the right offer on the building.

What do you usually budget on something like this?

Thanks.