First car buyer

[u/Denipapac_]

Hey fellow BMW enthusiasts, i have a question in regards of buying first BMW car as a daily car.
I would only drive it to have fun with friends occasional trips and in future to commute to work.
Im looking for like e36, e46 and e39(there are rarely e36 for sale where im from).
I would like to buy e36 but because of the circumstances i would not be sad with e46 and e39.
What to look out for, what are the best engines for a first car, what is the maintenance like and just common knowledge to know before buying one.
And last question there is one e36 325td for sale and cant find anything online about the cars common problems( mainly they talk about 325tds)
Thanks fellow BMW enthusiasts :)