-you need a platform that has access to securities from different countries
-you need a prime broker that can custody and clear these securities
-if you trade dollar neutral, you need a platform that does that
-You will need enough capital to cover margin on these securities, as there are no offsets
Cost wise:
-Ask about borrow rates for long stock
-Ask if your prime broker has a min rate for easy to borrow securities
-If what you trade is hard to borrow, ask for a sample rate for a simulated portfolio
-You will need to ask about execution fees-commissions, is it ticket charges or per share. Will you be on a route that avoids ECN charges. If not, does your strategy take liquidity on all the trades. That can add as much as 30 mils to your cost. On the sell side, you will have SEC 31 SEC fee. About $22/$1M sold.
Does that help? What broker do you use now?