To me the real problem with housing in Paris is, landlords request to see 2 years of tax sheet. When coming back from Australia, I just decided it would be too hard for me to find housing in Paris, and created my startup in Lyon.
Landlords are insane in Paris ! I had a friend who made 48k in his first job, he came from Grenoble and his parents weren't rich enough to "vouch" for him, so he spent almost a month before finding a flat, because landlords rejected him all the time, despite his salary.
With a diploma from a good engineering school and a previous work experience (internship and/or apprenticeship) the companies I talked about in [1] will pay you above 40k when coming out of school. With the two financial companies in the beginning being above 45k.
The main problem I see with developer employment in Paris, is the weight of the diploma in the remuneration. People with a university degree being offered around 30k most of the time.
Cost of living is pretty high (still less than London but the gap narrowed in the past few years). Count €1000+ if you want to live in a comfy flat in the inner city, which you do if you want to have reasonable commute duration, and enjoy the nightlife/culture.
I've been living in Paris for 3 years now, and before I lived almost a year in Boston, 6 month in Berlin and several month in London. Paris is really close to London on many topics (cost of living, commute time, nightlife, cultural events) but the quality of life is way better (weather, food) and Paris as a city is really beautiful. Berlin is really different from Paris, but really enjoyable also ! But eastern Germany's economy is still lagging far behind overall Germany and Berlin's job market is quite poor.
The biggest problem I have with Paris is the real estate, renting a flat is expensive but not extreme, but as soon as you want to buy something, it becomes crazy.
*salaries are usually counted before taxes. With a €40k salary, you'll earn around €28k after all taxes.