You can definitely make 8% yields here, but usually with new-builds in less than ideal locations (outer District IX or VI). Classic apartments in parts of V and inner VI tend to be better investments in my opinion, but have lower yields (6-7%).
There hasn't been any appreciation in Budapest in a decade, but that means that there haven't been any significant falls recently either. It totally missed the European property bubble of 6-7 years ago, but also missed the crash for the most part. Everything has fallen slightly, but new-builds and property which foreigners bought have fallen somewhat more.
There continues to be poor supply and lowish demand though, although good properties always sell when priced correctly.