Do I have to write instrumental 'scores' to get my music in films and TV Shows?
No way. Though plenty of instrumental music gets placed in films and TV, songs with vocals (of all styles) are in increasing demand by music supervisors.
Are my home recordings good enough, or do I need a "pro" studio recording?
Home recordings get placed in films and TV all the time. The instrumental and vocal performances must be good, and the recording quality needs to be reasonably clean, but you don't need 48 tracks and a live string section at the Record Plant to get your song placed.
How much money can I make?
That varies widely depending on the kind of show or film using your music. Money is earned in two ways: the licensing fee, paid up front to the writer/artist, and the performance royalty, which is distributed to the writer by a performing rights organization ( ASCAP, BMI, or SESAC in the U.S.).
The license fee is determined by the overall music budget a music supervisor has to work with, and the negotiating power of the artist. Unknown artists get far less license money than superstars, for example. TV shows and small films pay less than major studio feature films. A prime-time network TV show might pay a license of $500 - $5000 for an unknown artist - same for the smaller films. Major studio pictures pay well-known artists in the tens of thousands of dollars.
Performance income is determined by the number of people estimated to have seen the show and therefore heard the music. The more popular the show - the more money you make on performance royalties. A network TV usage might pay in the $1000 - $2000 range for one broadcast. You make new royalties every time the show is re-run, which is particularly good news if you've got music on a show that goes into syndication and airs frequently in markets around the world. Cable broadcasts generally pay less than broadcast networks (less viewers).
No performance royalties are generated on theatrical showings of films in the U.S.A. (though they are paid in other countries), but when the film is aired on TV, you would make your performance money.
You may also make money when videos or DVDs are sold, depending on the nature of your original license agreement.