BiggerPockets

#1 estimating repair costs

using bad comps
- comparing HOA to non-HOA
- comparing 1950's house to 1990's house
- making major value per square footage adjustments

not accounting for or underestimating "junk fees" you pay:
- property tax
- 4 sets of utilities every month
- insurance
- usually buyer's closing costs
- home warranty (what a scam)
- hard money lender junk fees.. they usually charge over 1k plus the points they quote
- cleaning lady

over fixing or under fixing a house
- every market is different, but we don't do any landscaping - it doesn't pay in my market
- we usually put a/c in, as that does pay
- etc etc
- the house doesn't need to meet your standards to live, it just needs to be better then the competition

trusting an un-educated agent to list it
- you don't want to chase the market down
- have the agent attempt to "double-end" the sale
- be too picky
- be not picky enough
- mismanage the sale escrows (a bad agent can let an FHA loan take 90 days. a good agent can get it done in 30 days).

Steve has a very solid list.

A couple to add:

-Not pulling permits
-Make renovations that appeal to the masses and not to your personal tastes

And the biggest (and probably most obvious) IMO:

-Overpaying for the property

50% on the deal is pretty unrealistic (purchase price + repairs). Unless you deal at a very low price point. Out of 75+ deals I have only done in the last 2.5 years, I may have done 2 or 3 at 5x%.

My first deal I paid 78% (purchase price + repairs) and made a pretty healthy profit.

1. Overpaying for the property is by far #!.
2. Underestimating repair costs
3. Not figuring in holding costs
4. Not adding in contingency expenses
5. Not properly evaluating exit prices
6. trusting others to do your job
7. Not having a good rehab team
8. Not having good team members
9. Not using BP Nation resources
and
10. Not listening to the good advice of seasoned pros

Buying outside of your geographic area is one I would like to add to the list.