Hey @Koshu Takatsuji, welcome to the BP community!
When it comes to buy & hold long-term rentals (LTR), you're typically talking about residential (single family and small multifamily) homes. While I've never heard anyone use the terms "buy & hold" for commercial, many commercial investors are essentially buy & hold investors who focus on LTR. So, if you're still deciding between commercial and residential, that's the first step. However, you probably want to start with residential since it's typically much easier to get started. You'll need less capital, less time and in many MSAs the supply of residential is much higher than commercial and competition is typically lower.
So, let's assume you want to go with residential LTR. Your choices now are single family (SF) and small (1-4 unit) multifamily (MF). The strengths of SF is typically that there is greater supply and less competition from seasoned investors. The strength of MF is that you get economies of scale. This just means that your expense ratio is typically lower since you have expenses that are split between multiple units (lawn care, roof replacement, etc.). Also, when one unit is vacant, you often still have the others pulling in cash so rarely do you have months of zero income, like you often do for SF.
The strategy you choose will likely be specific to the market you choose. Here in the Atlanta MSA, SF is arguably the one to go with as a new investor. MF is much harder to come by. With supply being significantly lower than SF, MF deals rarely hit the market and often trade off-market between investors. That being said, there are strategies that can allow a SF to act like a MF and create economies of scale, yet still have the strength of being easier to acquire. These creative strategies are gaining popularity as they allow what would have been a bad deal to become a very good deal with a 2-4x gross rental boost. One of these strategies is to purchase a SF with a mother-in-law suite or some kind of addition and rent out both sides, allowing for similar income to a duplex. Another is the coliving strategy, which is what all of my investor clients are doing these days. Essentially you rent the home by the bedroom and can even maximize rent further by turning unused common space into bedrooms. Fantastic strategy but not as straight-forward as renting out to one family. However, often it's those that work a little harder to learn the creative strategies that do well while others watch from the sidelines or settle for a couple hundred bucks a month in cash flow.
Now that you've chosen a strategy and property type, the question is - how do you run the numbers?
This may seem daunting but is actually pretty simple with the right tools and education. First, I would highly recommend hopping on youtube or watching the BP webinar replays on the subject. Pretty sure Brandon Turner has done a deal review/calculation webinar over a thousand times for BP members. You might have to wait for the next one if you aren't a Pro member. However, definitely recommend becoming a Pro member, at least for this first year while you're learning. This gives you more access to useful learning tools here on BP, like webinar replays. It also allows you to use the BP calculator without a limit. The BP calculator is great for getting started and learning as you watch Brandon Turner walk through deal analysis, but I would recommend finding a more robust, customizable one. I really like dealcheck.io and use that on all my residential deal analyses. You can even build you own with excel that will likely be better than anything you find online. Just hold off on doing that until you fully understand each piece of the online calculators.
Hope this helps a bit. Please, feel free to reach out anytime if you want to fire some of those other questions at me!
