Be prepared to potentially have zero income for many months.In addition, you will want to check the permits.  

@Jacob Hafer, in most cases its a sunk cost and some landlords nefariously even use the application fee as an additional income stream.

A lot of sellers are burned-out landlords who like the idea of "passive income"/mailbox money after years of chasing late rent payments, dealing with tenant BS and maintaining the property (I use quotes for "passive income" b/c no income is truly passive IMO, a wise seller will still pay attention to what's happening with the property in case they need to take it back, but collecting payments like a bank is generally easier than collecting them like a landlord, you can set up ACH with the buyer's bank or hire a loan processing company to handle it). 

One month or one decade selling a flip is an active business like selling hamburgers, and pays regular income taxes not capital gains.

@Gavin JexSo you want a bank loan and then seller finance as wellA bank would not be in second position so they as the owner / lender would be in second.Also 0% they would still be responsible for taxes on that at AFR so if your payment is $300/mo the loan would go off federal rates so they would essentially have to claim around $5k in interest income which would be ordinary income so they may end up paying all of your payment in taxes… just fyi if they did speak with someone on thisSounds like a steal if deal for you

There are so many rent controlled buildings that generate such little rent, with owners that paid 50-200K in the 70's that should be easy to turn into deals now.

Looks I have to report net income on SE Line 24 ($2k), but on Line 25, I cannot claim losses due to higher income (>$150K).

I have taken the wholesale and passive income course and started in March 2021.

Madrid have become the number one City in terms of income and investors since for the last 25 years investor friendly goverments in the region had atracted the bigger companies of the world to invest in the city.

My NET operating income (what actually matters) was 60k less than the year prior.