I did a number of seller finance purchases around the 2008 crash, just be careful not to over-leverage yourself and don't do close balloons (5 years + I would recommend).The worst position you can put yourself into is nearly 100% financing, a 3 year balloon,  and rapidly dropping prices (like 2008).  

I am the worlds best at offering exactly what a property is worth and simultaneously the worlds worst investor. 

If you learn from something that bit you... then it is a learning curve or from the school of hard knocks and not failure... unless you make the same mistake again! 

I already provided him a constructive feedback saying he was unethical and manipulative and didn't have my best interest in hard for the past 1 week and hope he understand his mistakes and give clear agreement on how we should work moving forward with terms to terminate the contact if we disagree on anything in the future.Let me know what you all think.

Also, look at the P&L from the last 12-24 months from the seller, compare bank records, rent rolls and receipts, etc. and see in in the worst month it was still a good investment.

I made all those mistakes you mentioned and more. 

My suggestion: Although I agree the market will stabilize, go for the worst scenario possible and if your numbers still look good, go ahead.

I work with a lot of house hack clients in Milwaukee.Here are the top mistakes to avoid: Don't buy small square footage.

If they don't change the fridge's water filter, the worst that will usually happen is they'll probably end up with funny tasting/smelling water.I have another lease that's a custom lease written up by an attorney, and has a clause that specifically addresses HVAC filters:AIR FILTER REPLACEMENT AND/OR MAINTENANCE RESPONSIBILITY [Landlord check this box if applicable]  The premises is supplied with a replaceable air filter as part of the HVAC system.

However, the worst thing you can do it force it and buy a property that doesn't make sense.