The BRRRR is a strategy... Buy & Hold, Fix & Flip, Wholesale are all strategies. You could also say they are systems used to grow your real estate portfolio. The key is to know what your strategy/system might be and learn. Expect to makes mistakes, however you can limit some mistakes by being around people that have done what you want to do. Join a local Real Estate Investment Association.
Build your team of experts who can give you advice on what to watch out for; Property Manager, Realtor, Title/Escrow Officer, CPA, Business Attorney, Tax Attorney, and Lender.
Before the crash investors forgot the most important rule of investing. Cash flow & Return on Investment is king and both should be a non-negotiable. Everything else; appreciation, depreciation, and tax shelters will come together over time.
I would start backwards with the lender. Sit down with a lender early in the process. Share everything about yourself; employment, income, credit, money in the bank, access to cash, and relationships you have like hard money or private investors. What your goals are both short term and long term. A lender is an Advocate of you. A experienced lender watches the national and local economy, they pay attention to real estate both from the purchase and sell, they know if the local market is a buyers or sellers market, what values are in different neighborhoods - if appraisers are coming in high or low on the values. A lender who deals with a lot of investors will know what the average rents are in an area.
A lender can help you determine what your buying power is, and help you build a strategy to access loans when you need them. They can tell you what the reserves need to be to refinance an investment property. This way you can make a good decision on buying a property, knowing what your cash flow might be and mitigate a crash. You can be ready for needing cash to close if you do catch a low appraisal.
The other thing a lender can do is be an accountability partner; meaning telling you if the buy is good and fits your goals or maybe on the outside and you should walk away. They know if the financing will be hard or easy based on the type of property you are looking to buy.
One thing to know is Fannie/Freddie do not have seasoning requirements currently. This means you can buy a home for $150,000, secure it with private money, fix it up, and then refinance the home easier than you think. A rate and term loan is refinancing the current note with no money back. If you are looking to take cash out (get your money back out) then you need to wait 6 months (no more) as long as the remodel is done and you have a rental agreement on the property or can qualify with the home vacant.
I am a lender so I am giving you advice specific to what I know and how I have helped other investors.
Feel free to message me with other questions...
Tim