With 400k one can startup a small boutique business. You can look for a small shop in the city where monthly rate is 10k. beg the landlord/landlady or caretaker to collect a year rate. If agreed, mathematically it means you will be spending 120k out of the 400k. Then you can use 80k to furnished the area and use the remaining money to get some beautiful clothes in Aba or Onitsha. atleast for men's boutique, the remaining 200k can be used to purchase 10 jeans, 10 Polo, 5 office T shirts.
After purchasing, put them in you newly rented shop to let people know that you are selling. Once you sold half of it, go back to Onitsha/Aba and purchase another one. continue like that until the business grows.