@cdw057
As @JimJ says real estate after sales is off the table here. Although I'm not actually quite sure what you mean, I reckon that in most places once you've purchased a property it's your problem. :-)
I'm also not sure why you object to the biggies. Usually, they're big because they're good. Even if you don't want to do the deal through one of the big guys, they're great for the initial research to see what you can get for your money in a particular area. I'd say BulgarianProperties (dot com) are good, as is Imot (dot bg), and Property (dot bg). You could also use RightMove which is a big UK portal with international listings, and they have a pretty good Bulgarian selection, many of which are offered by some of the smaller agents which you might prefer. Alternatively, you can go to OLX, which is a big listing site for Bulgarian owners and agents and is popular with the locals. But I'd say it's tougher to make a deal here, so it wouldn't be my first choice (although I have used it, and it's also good for research).
I would say, unfortunately, you might be disappointed. Turkey is still, I believe, cheaper than Bulgaria for both cost of living and property purchase. If you've got a fancy penthouse on a beautiful Aegean beach, you'll have a tough time thinking you'd made a good swap to a Bulgarian apartment on the Black Sea. I used to live on the Med in Cyprus, and I would love to have stayed beachside, but I was just grossed out by the Black Sea... and decided I'd go to Plovdiv instead, and just have a bigger city with easier access to mountains, Sofia, culture (former European Capital of Culture), and international travel.
However, I applaud your location choice (and your taste in apartments). Burgas is a good, large city, and being next to the Sea Garden is a fab location. But as indicated by @JimJ, this is getting into premium territory, especially if you want new (ish), big(ger) and penthouse-styley. I didn't even check the listings, but I reckon the nice stuff is already 3k euros / m2 and up in Burgas. (As that's around the ballpark in Plovdiv, Bulgaria's 2nd largest city.) You probably have to up your budget, or get a smaller/lower/older apartment, or look outside the city.
You can also go Sea Garden in Varna, but that's even more expensive. Personally, while I'd prefer Burgas Sea Garden, I reckon I might be able to find something interesting in maybe Sozopol (very nice town just south of Burgas). Or maybe one of the suburbs/exurbs of Burgas (such as Sarafovo, next to the airport) or Varna (such as Saints Constantine & Helena).
If you do decide to do a search, please note Bulgarian real estate is sold a bit differently to Turkish apartments. In Turkey (from what I've seen) they sell ready apartments, even when new. In Bulgaria, older apartments are (usually) ready, but new ones are sold as Bulgarian Standard - a concrete box for you to finish off (needing time and money). A new apartment at 2k euros / m2 will need another 500 euros/m2 (or so) to finish off. Also, the m2 here included a pretty significant chunk of common area, so if you really need 120m2 internal space (and 3 bedrooms) you're looking more like 140 or 150 m2 of gross area (per the listings)... or more like 450k euros (150 x 3k/m2), as my guesstimate. (And they usually don't include parking, so you also have to factor in your 20k per parking spot.)
Even worse, Bulgarian is not heavily into these larger apartments (i.e. 3 or 4 beds, 150m2 +) as they're not easy sells. There's a lot more folks wanting a one bed or two bed. This adds scarcity value to the equation too, especially if you then narrow it to the penthouses. By coincidence, my two posh mates in Plovdiv have exactly this kind of property, 3 bed/2 bath, 150 m2 ish penthouses, well furnished, in desirable city centre locations (one overlooking the Maritsa river, the other looking directly at Youth Hill). But pretty sure they'd be expecting 500k-ish (if they were keen to sell).
This is rarefied territory, and most Bulgarians would not spend that on a fancy apartment (even when they have plenty of dosh), as they'd prefer to spend such money on a house somewhere nearby (e.g. Markovo about 10km outside Plovdiv, in the foothills of the Rodopes). Some might also consider Bulgaria's "panel" blocks (communist era, I doubt they exist in Turkey, but you've probably seen them elsewhere in the former Eastern Bloc countries). These old buildings can look a bit shabby on the outside, but they often have pretty central locations, and they have generous helpings of green space and parking spots (i.e. don't have to buy one), and the flat's m2 doesn't include much common space (i.e. it's nearly actual interior). You can get big apartments, and inside they can be renovated to look like new.
I love Bulgaria, and I'm very happy here. But property has gotten pretty pricey. Turkey's pretty nice too, so you might just be getting a bit of grass is greener syndrome. Just give it a few days to pass. :-)