@Fredric Sjöberg Forewarned I'm new to real estate as well but through research I've found several things to be aware of when using the BRRRR strategy, but not knowing the lending or housing rules in Sweden none of this may apply
First when using the bank some banks here will not finance a deal if the condition of the property is not up to par. There are some Government programs that will finance the deal and lend you the money for the rehab on distressed properties but it should be used for your primary residence and not an investment property so this strategy is great when buying a multi family home and house hacking. I only mention this because to make the BRRRR strategy successful you need to buy properties under market value "rule of thumb at least 70 percent under" rehab them and through forced appreciation bring up the ARV so that way there is enough equity in the deal where refinancing makes sense and you can get more of your capital back out of the deal. This strategy works great if you can find the right deal and it usually is through buying crappy houses and rehabbing. When you buy properties at market value with the 15% down there probably wont be a lot of forced appreciation through rehab so when you go to refinance the new mortgage might cause you to cash flow negatively.
Second is finding a lender who will refinance for you, this is a process in itself some banks have seasoning periods which you have to hold the property for a certain amount of time before you can even refinance as well as other hoops to jump through so do your homework.
Short story long just make sure you find the right deal and analyze the property carefully, hope this helps