pbrosnan,
Which part of Sziv is it on i.e. which intersection is it closest to? 6.3% return is good. Sounds like you'll do fine if you stick it out for the long term.
Are there plans to renovate the building or has that been done already? The street is still a building site, with parts of it quite run down, but getting better bit by bit. Several loft conversions are in the process of being constructed, which means more renovated buildings and a nicer atmosphere for the people who live here. I wouldn't recommend buying a new build on this street though. IMO, in this area, you were right to choose an older apartment.
Many prices fell a bit in Budapest in the last two years, which what was inevitable after what was effectively a property bubble around 2003-04, fuelled by foreign investment. There is a lot of unwanted second-hand property for sale at the minute, usually in run-down buildings, which investors would have considered buying 2-3 years ago, but not now. It's hard to sell these but at the same time, it's also difficult to find a good classic apartment worth buying. They rarely even reach the Hungarian market, much less the international one.
You should call your accountant asap to sort our your tax issues! That's what you're paying him for.
Anyway, hope it continues to do well for you!