Yes, well said @Vasilev.
The problem is that many have heard of the "good old days" when the UK was part of the EU, and you could do a fast track Residency application with just your passport, proof of funds, and a medical insurance policy (or even your EHIC).
And, unfortunately, a few may have missed their opportunity during the transition period (the year 2020) due to Covid restrictions. I myself missed my chance to get my permanent residency in Cyprus as my flight was cancelled when Cyprus closed its doors last year.
Now, as for all non-EU citizens, it's a two stage process: we have to apply for the D visa first at our local Bulgarian embassy... and then apply for Residence when we get to Bulgaria.
You are quite right that, while the fee for the visa application is small, the overall cost, when you add your flights and accommodation, medical insurance, proof of Bulgarian home address, and so on can be significant.
Of course, you can do visa application yourself, but it often pays to have professional assistance as they know exactly what will get accepted. This is especially true if you can't qualify under the simpler categories such as student or retiree. I would not want to mess with a TRO basis without proper help setting it all up!
I used my Bulgarian attorney for my residence permit in Bulgaria and it took me one visit for 2 days, it just sailed through, easy-peasy. And my partner's permit came out a week later (my attorney submitted my family reunification application 5 minutes after I collected my residence card).
Meanwhile, I also applied (in 2018) in both Spain and Germany, as I had property in both countries. These I did on my own, as, I was entitled under EU law to get a permit. And the requirements (passport, address, money, medical insurance) were the same in each place... so how hard could it be? Despite multiple visists, my local German immigration office flat-out refused, so I didn't get it. While my Spanish one took 3 or 4 visits (with each visit having to be booked online, usually a couple of months in advance) because they complained about every single piece of supporting documentation (e.g. my Schengen insurance policy was in English, so they made me get a certified Spanish translation). I dread to think what it would be like now, trying to get the German or Spanish equivalent of the D visa!
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