@Ryan Rogers There's no such thing as zero vacancy! If you are using a zero vacancy as the basis for your calculations, you are setting yourself up for failure in this business. Keep in mind that there are two kinds of vacancies, physical and economic. You are NEVER going to be able to avoid either or both of these over a long period of time.
As I pointed out, at some point you will rent your house to a professional tenant. He's well dressed, speaks well and has good references. After you receive the first months rent and deposit, the second month's check will bounce, followed by many excuses, deaths in the family etc. You buy the first couple of excuses because they are credible sob stories (and you haven't heard them before...). Once you start the eviction process, you find out that the tenant knows all of the inns and outs of the local eviction laws, postpones the hearing (perhaps over another death in the family...), claims habitability issues in the house (that he caused), requiring another hearing in a months time etc. By the time you actually get the deadbeat out, you're out 90+ days of rent. If you're lucky, there's not too much damage to the house, but you will end up painting and replacing the carpet. This is known as economic vacancy, there's someone in the unit, but you are not receiving rent. There's a small percentage of tenants that fit into this category, but if you rent units for long enough, you will step on one of these landmines eventually. If you have been in the business for 30 years and have 100 units when you do, it's not that big of a deal. However, if it happens to be your first tenant after you bought your first property, a $500K house with no money down, it can be an absolute disaster.
As to your next question about not counting on appreciation. I have owned multifamily properties in San Diego since 1999, enough time to see some ups and downs in the market. I count on cash flow and forced appreciation, never on market appreciation. I can control cash flow and forced appreciation but I have no control at all over the market in general. What is the point in speculating that in 20 years, my portfolio might be worth twice of what I paid for it? A "feel good" exercise? It's so far out and with so many variables that the number becomes irrelevant.
I like to focus on the here and now. What is this building worth today? Can I buy it for less than what I think it's worth? If I have to pay full value, can I negotiate favorable terms on the financing? Once I own the property, the focus is on what can I do to improve the cash flow from the property? What can I do to keep it from deteriorating? What can I do to make it look better? Can I raise the rents? All improvements can be checked against the potential increased cash flow by dividing the cash flow with the prevailing cap rate in the area. For example: It will cost me $10K to rehab an apartment; I can raise the rent by $200/month after the rehab; increased cash flow is $2,400/month; cap rate in the area is 10%; $2,400/.10 is $24,000. So, if I put in $10K, my building will increase in value by $24K; that's a good return and I would probably do it.
If you are projecting long term increases in value in order to compare your investment with the stock market, you are missing a crucial differentiation, real estate is not a passive investment. You need to manage the property, or manage your manager. You need to stay on top of maintenance, drive by the property on a regular basis and make sure it's still standing and that the curb appeal is preserved. If you buy the house today, expecting not to touch it and have it be worth $1M in 20 years, you're in for a surprise...
Market appreciation happens, but don't count on it. Use it to your advantage when possible, sell properties when the market hits a high, buy properties when the market crashes. Looking at long term value charts can be helpful, but don't forget that there are many external factors that can affect the appreciation trends, such as inflation, quantitative easing and demographic trends.
Let me finish by making an analogy between learning to invest in real estate and learning to swim. You can start by jumping in at the deep end and hoping you figure everything out before you drown. Some people have actually done it, survived and done very well for themselves. Another alternative is to start in the shallow end and gradually increasing your depth as your skills and comfort level improves. Your chances of survival and success will dramatically improve, even if it's not as exciting as the first option. Buying a $500K SFR, with no money down and no cash flow, hoping for appreciation is the equivalent of trying to learn to swim by going to the pool in the middle of the night, with no life guard, not knowing if there's even water in the pool, jumping in at the deep end and hoping you figure it out before something bad happens.
Start at the shallow end my friend, it won't be as exciting, but chances are that you will still be here in 20 years.
Erik