Building the Stadium

First the costs, since these are not spelled out in the game guide.

Cost to construct a level in a percentage range:
0-9 $ 200,000
10-19 $ 400,000
20-29 $ 600,000
30-39 $ 800,000
40-49 $1,000,000
50-59 $1,200,000
60-69 $1,400,000
70-79 $1,600,000
80-89 $1,800,000
90-99 $2,000,000
100 $2,200,000

Days to build:
0-24 1 day
25-49 2 days
50-74 3 days
75-99 4 days
100 5 days

Costs to maintain:
Take the percentage level and square it, then multiply for the multiplier for that facility (below).
Training 60
Regeneration 60
Cheerleaders 70
Scouting 70
Marketing 70
Youth School 80

Example for 10% Training Facility
10 (Level) x 10 (Level) x 60 (Multiplier) = $6,000 daily operating costs

Additional Info:
(The basic purposes are well spelled out in the guide)

Your training facility is the most important feature. Because of the way training works every player on every team is constantly improving. If you can not keep up with the rate of training of your league, your team is effectively getting worse until it is demoted. The key to success as you start out is getting a core of young players to train and build around. A a good Youth School is useless if the players receive no training when getting out because they will certainly not be ready for the starting lines.

Regeneration is discussed in detail in the energy article. This facility is the source of it. The higher you build it, the more you can ask of your players.

Cheerleaders boost player motivation. The higher it is, the better they will play. They'll also keep your team spirit high because you won't have to use high importance as much.

Scouting has the least visible return for your money, but it's well worth it. Better suggested ticket prices will increase your income. High scouting is essential for player decisions. Low accuracy could mean letting a top youth player go or spending millions on an older player who's already finished.

Marketing increases revenues by increasing attendance, fan club membership, sponsor fees, and merchandise sales. The investment pays for itself.

Youth school gives you the players you need to build your team. While quality and potential are independent of level, starting AI rises with it (along with the number of players). If you build your school enough, you'll have players that can be sold as soon as they hit 20 for a healthy profit, even if they'll never make your starting lines.