If you're handy live-in flips can be a killer way to get started!

Heating costs can be a killer on larger buildings with central boilers, especially in colder climates.

Look at insurance and tax costs, those two items are the biggest killer of cash flow.

But the question I find myself asking in this circumstance is, why would I spend the time and effort to find someone else a killer deal for 10K, when I can try to wholesale a deal for myself? 

The HOA fee seems to be the killer.

I'm a Realtor with a couple properties listed in Boise, ID and a neighboring town for my investor/client that are currently rented as co-living or rent-by-the-room and getting killer income. (7.3% - 9.5% Cap rate) So far, every inquiry has been baffled by the concept of co-living or rent-by-the-room and immediately ask if they're being run as a halfway-house (which they are not).

There are not going to be many killer deals on the MLS and yet I think most investors mostly purchase off the MLS. 

Quote from @John Ma: 70% ARV is a killer deal in our market. 

I am not an expert on the spanish tax system but I am reading upon it - It appears that your worldwide assets(Properties in the US) would be subject to Spain's 'Wealth Tax'.Spain is a great place to live...but their tax system is killer

Most land buyers who are developers usually stick to a very predefined region within their local market and they hunt and wait for killer deals and market swings to get the land they want for the very specific purpose they want.