The idea is to not have too much asset/equity in one LLC. Let's consider following:
Your house is cash offer, no loan, then you might want to limit maybe 100K capital in each LLC. If each house is 100K, then you might consider one LLC for each house.
If your houses have loans, then your equity is much less. Say you have 4 houses, each worth of 100K, with 20% down. You essentially have only 80K in. So, might be enough to have only 1 LLC.
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