Lucrative means bringing in a great deal of money. Profitable, and rather more so than expected.
It describes deals, contracts, careers and sidelines, so a lucrative contract and a lucrative career are both standard. The word is neutral on the surface and often carries a faint suggestion that the money is out of proportion to the effort, which is why lucrative sidelines sound slightly suspect. It never describes a person, only what they do. Profitable is the plainer word and remunerative the more formal one.
1adjectivelucrativeProducing a large amount of money.
“He gave up a lucrative career in the City.”
Lucrative is about gain. Latin lucrum meant profit and gave lucror, to gain, which is the same lucre that English still calls filthy.
Proto-Indo-European
*leh₂w- — profit, gain
Latin
lucrativus — profitable
French
lucratif
English, today
lucrative
Built from
French lucratif, from Latin lucrativus (“profitable”), from lucratus, past participle of lucror (“to gain”), from lucrum (“gain”), ultimately from Proto-Indo-European leh₂w- (“profit, gain”). Compare Spanish lucrar. by surface analysis, lucre + -ative.
Etymology from Wiktionary, CC BY-SA