"Mortgage Must be Assumed" & "52% of sale price downpayment" Why?

[Bill E.]

I've recently reviewed an apartment complex that looks interesting however the current mortgage must be assumed. Also, the deal is requiring a downpayment of $1,175,000 (52% of the sale price - asking price is $2,250,000). The current mortgage balance is $1,075,000 fixed at 6.25% due in April 2016 and amortized over 25 years.

Here's my questions - any insights would be greatly appreciated

1. Why must it be assumed - is there a pre-payment penalty?
2. Why must there be a 52% down payment?
3. How is the mortgage factored into the purchase price?
4. Could this be refinanced somehow?
5. How do you see this making sense for a buyer? (i.e. would a buyer assume and then refi if possible? Offer a lower purchase price to make up for the higher mortgage interest rate?)