Yes, I have to deal with two currencies on a regular basis, the Swedish krona and the U.S. Dollar. I have income in one (PhD) and debt (Student Loan) in another. This means I have to consider how I am going to pay my expenses on a monthly basis, both in Sweden and in the U.S.
Aside from having to deal with two currencies. I have to deal with due dates of everything and consider the value of the currency being transferred. These rates fluctuate regularly, to the point that waiting 5 minutes could mean an extra couple of dollars. For this I use Transferwise. This method is the cheapest, especially when comparing wire transfers done through a bank. I have saved a couple thousand dollars on fees, as well as getting a better conversion rate.
The due dates is something I do have to consider. So, I pay my student loan with the money I transferred the previous month since it is due the 12th and my transfer takes 2 days to finalize after my pay date (approx. the 25 of every month).
First things first, I know what my debts are: the main one is my student loan. It is through Navient and I consolidated it in 2016, the total amount was approx. $60k. I took this loan out so I could get my Masters degree. There are a few reasons why I do not regret this. mainly because I had the opportunity to live in the U.K., and attend one of the best universities in the world. This was the University of Oxford which was ranked number 1 in 2020. I will write a in-depth post of why I chose to go abroad for this degree, rather than staying in the U.S.
I do not have credit card debt, however, I still use my U.S. based credit cards (I personally like Chase). In addition, I have a Swedish-based credit card, and I pay it in full monthly. This avoids all interest fees.
Credit / Income
The whole point of reaching FIRE or reaching financial independence is to have the freedom to make a choice in how you live your life. Another thing you learn is that you have to have multiple streams of income in case something happens to your main source of income. So I have several types of income that are active and one that will be passive once I have a large enough nest-egg.
So, my main income is from my job as a PhD student/researcher. Then I also have income from reselling. or selling items I no longer need. I also conduct tours through AirBnB experiences but since the pandemic started that has died down significantly. Additionally. I am building up my brokerage portfolio so that the dividends I earn from that will sustain my lifestyle. However, that takes time to build up and it will not be ready within the next few years but I will keep going.
What you need to realize is that anything can change in a moment, so realize that your FIRE number is not set in stone. For instance, my lifestyle may change depending on where I move because my number does not include car costs or health insurance. It is assuming that I have the exact same life I have now, but that is subject to change.