Entry level bike for 140kg rider - what features to look for and what to avoid? I am a fairly large person (140kg). 7 years ago I used to bike quite a lot (I would go everywhere every day on the bike). Back then I weighed much less (I also was much younger, now I am 20 years old). 
I am looking to buy an entry level bike (is around 250 euros but I can go higher, which is a decent sum in Romania). 

My question is: what should I look out for in choosing my bike in order to be sure that I am buying a bike that will last me for some time: what parts that tend to be most affected my the users' weight should I check, what dimension for the tires (I am 1.90 m tall) etc. 

I will mainly use it to go on normal, asphalt, roads, so I don't require something that is sturdy from that point of view. I plan on using it almost as much as I used the bike back then.
You should buy a touring bike. Whereas a regular road bike can accommodate a person weighting 100kg, a touring bike can accommodate a person weighting 100kg and also 40kg of cargo. So, without cargo, a touring bike will accommodate a 140kg person.

Needless to say, avoid those low spoke count wheels and select 36-spoke wheels. There is absolutely no reason to choose 32 spokes unless you really have to. Less spokes than 32? No way! (Although I have to say you can get away with 32 spokes on the front wheel, but I don't see the reason for making such a strange choice.)

Unfortunately, such quality bikes cost starting from about 1000 EUR, not about 250 EUR. The one I have has been built myself from the Long Haul Trucker frame: http://surlybikes.com/bikes/long_haul_trucker but I wouldn't recommend building a bike yourself unless you really want to learn how bikes work.

I don't believe you can find a decent touring bike as new costing only 250 EUR, so your only options are to increase your budget or to look for used touring bikes.

If you find your seat post slips due to your high weight, buy a big honking seat post clamp: http://surlybikes.com/parts/small_parts/constrictor

If you find the spokes don't stay tight, first have a competent mechanic adjust spoke tension and true the wheel, and if that doesn't help, buy some good quality rims and have new wheels built. The wheels I built myself use these rims: https://www.rosebikes.de/artikel/xtreme-sari-t-19-r-28-atb-felge/aid:46903 ...that absolutely can withstand a 140kg person, provided that the spokes are tight. Unfortunately, they don't seem to offer a 36-hole variant anymore (I bought them when 36-hole variant was offered), so that may necessitate making the strange choice of 32 spokes. Use DT Swiss Alpine triple-butted spokes in the 2.0mm variety if you need to have a new wheel built.