I'm sure there are a lot of details that I'm leaving out.  

He will almost certainly not opt to cure (the expenses will be rather large).I have been told that, in commercial deals, it is simply a take it or leave it proposition and that price changes are not negotiated after the contract is signed.

I am interested in buying a relatively low cost building and I am not worried about financing, but I am still shopping for mortgages and would like to leave my options open.

Can I replace one residential mortgage with another eventhough selling my home would still leave me with 4 total mortgages?

You'd most likely have a hard time getting another good tenant to replace them if they leave.

I have been interested in real estate investing for many year and I hope this is the place where I get enough information in order to begin investing and with time be able to leave the rat race.I look forward to learning from everyone!

There is no practical way to evict someone, I had to pay a renter to leave.

Settle the security deposit in the customary way you would do it for any tenant that leaves.

Most people like to see 2% but not possible in all markets.Based off of the $1400/mo rent, using the 50% rule $700 would go out in expenses such as taxes, insurance, vacancy, maintenance and repairs leaving the remainder for debt service and profit.That would mean $8400 NOI Est.  

if you borrow 400k at 5% with a 20 year am your payment would come in @ 2.639k  leaving you a cash flow of roughly $900 a month.If you forgo the 1031, eat that tax and and invest the 250k you should be able to get a 4 plex, rented at 550 per unit yielding 2.2k in gross rents netting 1.1k (using the 50% rule) but you don't have all the other units rented out and tenants paying the mortgage for you building equity.Note these are rough numbers but my wife recently helped a client buy a 8 plex here in PHX and the buyer looked at a lot of properties over an extended period before finding one that worked  for them.