There is money to be made in buying Leicas if you find a real steal at a garage sale or live auction, but not by buying from knowledgeable dealers. There is even less chance of making money when buying on credit. My Leica M4 body cost about $200 overseas in 1970 when my base pay was $4 an hour. Now it might be worth somewhat more after 42 years of hard service. I consider it a bargain for the many thousands of photos taken with it, but certainly not for its intrinsic value.
Going into debt to make money might work for a very few people who really know what they are doing, but not for most of us. There are a lot of sharp people and corporations in trouble because they thought (or hoped) that they knew enough to beat the few experts at that game. Staying out of debt is safer and wiser. Constant studying will help one to recognize a true bargain on the rare occasions when they are found.