Little bit confused why you would even consider buying a flat right next to an industrial estate in what is - rightly or wrongly(see other threads) - still considered one of Berlin's grottiest neighbourhoods. No wonder it's cheap. Sounds like your chances of reselling would be close to zero.
On the floors issue, another thing to bear in mind is that 'erdgeschoss' flats, though often cheaper, are difficult to sell ( ground floor/or on the street). And something on the ground floor of either Wedding or Neukolln is gonna be doubly difficult, that's for sure! Being up high doesn't tend to bother Berliners, I don't think, although no lift sounds a pain in the ass.
Thy whys and wherefores of buying property in Berlin is a complicated issue - covered in plenty of other more specific threads, I think - and you certainly WILL find some that back up the estate agent hype ... ie that the prices can't really be lower, and that Berlin is increasingly high-profile and desirable place to live. So MAYBE a good investment. BUT there's lots of caveats to that. Firstly, new, wealthier people moving to Berlin largely want to live in areas such as Mitte, P'Berg,
Schoneberg, Charlottenburg, Friedrichshain, or
Kreuzberg. People with less money are going to have plenty of opportunity to pick and choose a place to rent for a long time yet. UK house prices are high because there are not enough places to go round. The opposite is true in Berlin. Don't necessarily expect a boom in the population here either - in the 90s following the post-unification euphoria the government confidently predicted the population would shift from 3.5 to 5 million people by year 2000. It never happened. The population actually declined, and is still only hovering around the 3.5 million mark. Point is, it will be a long long time before people have to fight for space in Berlin... if ever. And whilst that's the case, most people will rent - and those that seek to buy will be choosy, and want an altbau in a 'good' area.
The only reason to buy in Berlin is if you are in love with the city and life here. Not as an investment opportunity.
Don't want to be the prophet of doom here guys!! I've been through the same process myself - my partner and I were offered a 55m flat, perfectly nice in good area etc, for 51000 euros, which back in Autumn last year was only about 36 grand sterling. Coming from Brighton, where BEACH HUTS go for more, we were sorely tempted, and scraped about 40per cent of the price together and looked into financing. But the more thorough our research, we found a number of reasons why it would be better just to rent ( and enjoy the money!). And this was a flat on the border of Schoneberg, two mins walk to the Tiergarten. In London, the very proximity to, say, Hyde Park, would add another few zeroes onto the price. Not here.
Maybe your situation is different, and you have lots of spare cash - in which case, well, maybe it's worth taking a punt. But think it through - and definitely check out the areas first. Berliners are very picky/loyal about their "kiez" or neighbourhood, more so than the English - think of Berlin as consisting of dozens of little micro-neighbourhoods. Some of these are highly in demand - others people wouldn't touch with a bargepole. Confusingly, sometimes they are even next door to each other! Get to know the vibe first.
Whatever happens, good luck, and if you move here, have a ball!