I will take a stab and assume you mean that as landlord you charge full market price, but take payment in the form of a convertible. This arrangement is fair only if the housing is comparable to what the entrepreneur would otherwise be paying cash for. Otherwise the landlord is getting screwed, or the entrepreneur is too loose with the equity.
As an investor I hate convertible notes- there's no way I would ever agree to this sort of arrangement unless the conversion price was capped.
The form of payment is independent of the price you charge. The advantage of using convertible debt is you do not have to decide on valuation. Many people on both sides (investors and founders) would find this preferable, precisely because putting a valuation on a very early stage startup in a fair way is nearly impossible.
FWIW, pg suggested using convertible debt in such a scenario although someone else on the same thread links to a counter-opinion. http://news.ycombinator.com/item?id=565493
The "advantage" of delaying an assignment of valuation exists only for the founders. The only reason investors sometimes prefer a convertible is because it's simpler and therefore lighter on the legal fees. Otherwise it's insanely bad (if uncapped).