It can be hard to find a *qualified* tenant, but generally speaking it's not hard to find potential tenants as applicants. If you're not getting any callbacks on your rentals it's likely you're priced above market. The way you prevent that situation is you figure out what prevailing rents are in your area and you price your rents accordingly.
This is not to say that you rent your unit for the mathematical average of rent in your area for a unit of similar square footage. Amenities matter. If your unit (or building) has more amenities you'll rent towards the top 20% of rents in your area. That is, assuming amenities and the desirableness of the area justify it. Similarly, if the apartment has seen better days and the area is sketchy, you'll lower your price to compensate.
Side note: you may want to read a book called Economics in One Lesson. It covers free market economics in an approachable way that won't bore you to tears. If you prefer audio books, it's on Audible.
New landlords often struggle to find *qualified* tenants that:
1. Have a reliable income source.
2. Have credit scores that suggest they pay their bills on time.
3. Don't have evictions in their history.
4. Don't have anything alarming in their criminal history.
5. Aren't going to beat up their unit.
Things to watch out for:
* Potential tenant is willing to pay you several months worth of rent up front. This is a big red flag and a sign of a "professional tenant." It's also the oldest trick in the book. Often, a tenant will pay those first few months in a large check or money order and then stop paying entirely. Tenants who do this have been evicted before (often many, many times) and may well know eviction law better than your typical eviction attorney. This can translate in to many lost months of rent.
* Large numbers of unrelated people sharing a lease. Sometimes this is normal, such as in an area that rents to college students. It's not a red flag by itself. But, a common issue is for several lessees to move out and stiff the remaining lessees with the bill. The remaining lessees will contest saying, "we can only pay x% of the rent this month." If you accept partial rent you may not be able to evict for the month in which you do. Also, you can end up with "musical tenants" who come and go in such numbers that it's unclear who is actually living in the property. That makes evictions harder and more costly.
What most landlords do is get something called a "joint and several liability clause" inserted into their rental contract. This makes every occupant equally liable for the rent. Also, savvy landlords will insert language into their rental contracts that basically say "nobody can live here that the property manager hasn't done a background check on." There is usually a small exception window of about a week to cover short term guests such as visiting family.
* Potential tenants with dirty cars. Messy is not a protected characteristic. If someone's car looks like they trash the interior, it's highly likely they'll trash your unit.
* Acts like an entitled a-hole from the start. A-hole is not a protected characteristic. If, during the rental application process, the applicant cops an attitude or behaves abrasively towards you or your management staff, it's a good sign they're unhappy with life and want to drag others down to their level of misery. Feel free to skip them.