Great idea
However, adding a kitchen may cost you.
The cost will include
A. cabinets, 1.5k
B. appliances, 1.5k
C. electrical/plumbing/gas work, 3-5k
D. general work (floor, wall etc), 2.5k
Total: 8-10k
The C+D items will vary greatly between contractors, quote from 2-3 contractors with good reputation will make you comfortable.