Sonu, the first thing you should do is follow what most people in this forum are saying and get a cheaper house. It is not impossible to get a house for 25k in parklands or westlands...it won't be the newest block of apartments but rather something built in the 60's or 70's.
Owning a home in parklands or westlands is prohibitively expensive...average apartment prices for a 3 bdr are 12-15M. The high prices are due a shortage of land and the increased demand in the area. Instead of focusing your interests in westlands i would suggest looking at areas distant from the cbd yet having good transport links...thika road is the best option right know thanks to the super highway being built. Although these areas seem very far from "nairobi" today, they will be an integral part of nairobi within a few years. I'll advice you to buy a plot of land and let it sit for a few years and meanwhile save some money to build the house. Don't be stigmatized leaving next to africans...if you become incredibly rich you'll build a mansion in old muthaiga and your neighbor is most likely to be rich african like Kibaki.
You should also focus on increasing your monthly income. Has you wife considered working? If she can get a job good, if not she can start making snacks and start selling them to friends and relatives...thats how house of manji started. It would also be advisable for you to look for supplementary source of income...import clothes and gift items from india or dubai, become a photographer or do some freelance work in your own field e.g if you are an accountant you could start keeping accounts for small business on the side, this is something you can do on the weekends.
Wish you the best, but turning your dream into reality is ultimately your job.
Before you can be be old and wise, you must first be young and stupid.