When you invest in occupied walls, you seek to make the best possible investment according to your objectives, to do so you must not only see the immediate return offered by the tenant in place and for various reasons.
First, it can go according to the terms of the lease or go bankrupt, if you bought too expensive (with an over-rent), you will be forced to re-let at the market price and your yield will automatically drop.
Then you too will one day be called upon to "arbitrate" (assign your property), your potential buyers will be notified and will not be focused solely on the return (see the article on "how to calculate a return", which explains the difference between yield and profitability).
Finally, because you buy an occupied property, therefore with no real possibility of optimizing the current income (except in the case where the property is partially occupied), but this can present a potential for creating value when it is free ( without tenant). For example, you could buy an occupied warehouse in a residential area when the tenant leaves you could sell your property much more expensive to a developer. Another scenario, if you buy occupied walls with a large surface area, when the tenant leaves, you could divide your investment into smaller areas to increase your yield or sell by the cut.
In conclusion, performance, even if it is your entry point on a file, should not be your only analysis, the study of the location, the current tenant and the exit scenarios must be studied.