As it stands, is 26 : -

Non homegrown (18) ONE NEEDS TO GO!

Kepa
Caballero
Azpilicueta
Alonso
Zappacosta
Rudiger
Emerson
Luiz
Kante
Bakayoko
Kovacic
Pedro
Willian
Jorginho
Hazard
Morata
Batshuayi
Giroud

Homegrown (no more than 8 if you have 17 non-homegrown)

Cahill
Christensen
Fabregas
Drinkwater
Barkley
Moses
Loftus-Cheek
Green

U21/Academy (as many as you like)

Ampadu
Hudson-Odoi
Abraham
Musonda