@bigboss...
First let me correct you, a wedding doesnt have to be expensive, actually it can be a very private affair, and very cheap.
If u dont want elaborate wedding then this is an alternative:
1. Go to Ag's sheria hse, room 211 with a copy of your ID and her ID (I have assumed u are a man)
2. Pay Ksh 200 and fill the form they will give you.
3. Go back to the same office after 3wks, this time with her.carry your original IDs.Pay Kshs 1550 and they will fix a 'marriage' date for you.
4. Get married, get the wife and the CERTIFICATE. carry a ring (optional) and two witnesses, one for each.
DO NOT Divorce after that...pplleeaassee
"Peace is our profession, War is our business" ...Unknown