If a project has only a $20 k to $30 k profit, I don't feel there is enough buffer if a cost overrun occurs. 

I would probably shoot for 70-75% to create a contingency buffer... you will probably overshoot your rehab budget b/c of the emotional component of it being YOUR home.

I would live with roommates, cut expenses, and increase your income to give yourself a buffer. 

I would figure $150k on renovation to give you a buffer. 

Every deal is different, but yes you need to keep all of that in mind.I was only referring to the rehab part of the deal structure, saying you should include a sizable buffer for extra rehab costs on your first few deals.Things like closing costs and holding costs like taxes, insurance (vacant property insurance if you won't be living there), utilities, private/hard money interest, etc. are totally separate and need to be factored into your purchase price also - unless you like losing $ or working for free.Oh and don't forget to include your PROFIT in your calculations - if you don't factor it into your purchase price, it won't be there when you sell.Basically if you are going to "fix and flip", you need to (as Steven Covey said) "begin with the end in mind" and start with comparable sales ("comps") for similar properties (same area, same type of property) sold within the last 6 months, to determine "after repair value".Then you subtract your closing costs to buy, holding costs including loan interest (I would plan for 6 months on your first few deals even though that's generally on the high side), your rehab costs with a significant buffer for error, closing costs to sell (including agent commission - don't kid yourself that you're going to sell it without an agent), and your desired profit.That gives you your "maximum allowable offer", which should not be your opening offer to the seller/bank.

Do I have too much buffer in my numbers, not enough?

As such, it was probably bad luck of the draw, and you hit your four star before you had quite as many five stars to buffer. 

Keeping some type of emergency fund is important to have a buffer.

If you can scale it quickly, perhaps it may work better but $150 of buffer between profit and loss doesn't leave a lot of room for a $4k A/C replacement right after you have had another major expense.

Since I'm new to this, I figured I would create as much of a reasonable buffer as possible, and start scaling down from that number.Last year we refi'd into a nice 15 yr with a very nice rate, so another refi is out of the question.