when you renew your lease for another year at your apartment complex do you have to show income and have background check run again etc.?

No. They may choose to run a background check again but, it is not usually done.

Its completely up to the landlord. Most landlords aren't diligent enough to do so, but some are.

It is not required as you have already done the credit checks. You are just renewing your lease.

Rarely but they can request this (and if you refuse they'll likely just turn down your renewal). This may be a sign either that they aren't sure about you as a tenant, there is new management, or possibly that they've just had a lot of problems with other tenants recently so they want to check everyone (but heck it could also just be their way of doing business ie means nothing).

If the landlord wants it.

Not usually

Usually not, unless you live in an "income restricted" or Section 8 complex.

For a non-subsidized rental, no. A landlord might request it -though it's pointless - if you've done things that make you a risk for non-payment, why offer a renewal? But you can refuse. You won't be renewed, but you don't have to provide any information.

Background checks cost money. You pay for that as part of your initial application fee. I have NEVER heard of a landlord requesting updated employment information from and requiring a new background check on an existing tenant for the purpose of offering a renewal of the lease. Why bother? Just don't renew the lease, if the current tenant worries you to that extent.

If the rent is subsidized, the agency providing the subsidy may demand information from you. Usually, it is a requirement that you immediately report to them any changes in employment and income, as these things have a direct impact on the subsidy you qualify for. But it would be the agency doing the asking, not the landlord.

If you have a good history with the landlord, they usually will just renew the lease. If you are a problem tenant, they just will give you notice and not offer renewal

Sometimes