Are police checks and blood tests manditory need to know exactly what the requirements are for passport and visa
Need to know cost of each?

Nope, normal request for money when a SCAM is involved..

Normal visa and passport is about 300 dollars total. Since you have not actually traveled there and have not meet this person in person, they will have to travel here on a tourist visa and then when you get married, apply for a change in status.

There is no medical required ( and if it was it is about 105 dollars) there is not police report, (but if there was it would be about 50 dollars)

The passport is gotten from their government, and they can get it in about two weeks, one if they pay for the rush, The VISA comes from the US department of immigration, they need to contact the US embassy in their country.

There is no ( and you did not ask, but this is next on their list) a bank account with money in it, required to travel on.

Airline tickets can be bought pre-paid, so you may buy the tickets online and they have to show ID to pick them up. You can make them where they can't cash them in.

Ghana is the largest area for dating fraud.