I was hour building recently at one of the west coast schools that advertises in the local flying magazines here in the UK. Although I was doing single engine I inquired about doing multi time on a later visit. From what I remember they only required you to have 15 or perhaps it was 25 hours total multi time before you can go off solo without a safety pilot. It sounds like you have already committed to Ari but if you are looking for additional time at a later date I would really do some research as different flight schools have different insurance companies and policies and like most things in life there are deals to be done.
As an aside I think the rate for a Seneca was around 130 USD wet.