I'm considering purchasing a condo or a small SFH in the Oceanside/Carlsbad area as an investment property and renting it out on a short term rental site like AirBNB. 

@Ofir R.Recommend you first figure out the property Class you want to invest in, THEN figure out the corresponding location to invest in.Property Class will typically dictate the Class of tenant you get, which greatly IMPACTS rental income stability and property maintenance/damage by tenants.If you apply Class A assumptions to a Class B or C purchase, your expectations won’t be met and it may be a financial disaster.If you buy/renovate a property in Class D area to Class A standards, what quality of tenant will you get?

-------------------------------------------------------------------------------------------------------Recommend you first figure out the property Class you want to invest in, THEN figure out the corresponding location to invest in.Property Class will typically dictate the Class of tenant you get, which greatly IMPACTS rental income stability and property maintenance/damage by tenants.If you apply Class A assumptions to a Class B or C purchase, your expectations won’t be met and it may be a financial disaster.If you buy/renovate a property in Class D area to Class A standards, what quality of tenant will you get?

I recently purchased my first duplex in Peoria, AZ in September and I am using it as a house hack where I rent out one side and live in the other.

To me a house hack will most likely work in Tulsa - I haven't done any research on that area, but as far as I know it's not a crazy market like places in California etc.Also read a lot, get some books from your local library or purchase some online.

Every house I have purchased was sold "as-is" (good opportunities) and had no bearing on the deal.

Before seasoning period ends, I want to sell to my younger brother who purchases with conventional mortgage.Is there anything wrong with this idea?  

@Anthony Wick hey Anthony, not the first property we have owned, I sold a duplex to help pay for most of this purchase, and have a home in Park City Utah that has a mother in law apartment.

I'm 23, and I'm looking to purchase my first rental property this year.

Three out of my first five purchases were from the MLS.