You can get by with 5 or 6 out if they include Pinny, Mansion, SIA, Matchbook.
Find them pretty much every day, sometimes they last 2-3 days or longer in football.
Generally you rarely find better than +100/+110 (or equivalent) which is a 2.4% return if you have no opinion and take the money irrespective of who wins the game.
I don't get too exicited if I can't get a 5 cent difference unless a side is also involved. For example last week Carolina -1, +118 (2% fee on wins) was available at Matchbook while Tampa +1.5, -110 was widely available, so a Carolina win by 1 would give a push and a win, while you get about 1.3% return with any other result.