121 and 1031 multifamily question

[Royce Talbo]

Hey guys, I bought my home for $550k its a 3 unit multifamily and I plan on selling for $800k.  My tax person splits it 50/50 due to sq footage.  So my gains will be about $250k, which from what I understand i can do a 121 for $125k and 1031 for the other $125k.  

My question is, since I am only using half for 1031 do I have to find another property that is $800k or can I find a property for $400k or 2 $200k or 4 $100k properties?  

Also If the latter applies from my previous question, after I acquired a new property(s) can I refinance or get a HELOC to get money out? And how soon can I do it? For example (not including closing cost) I could only find 1 $400k property within the 45 days. I put in the $125k giving me 31% equity. I refinance or get a HELOC to get it down to 20% equity ($80k) and later find another property for $225k to put down the remainder $45k as a 20% downpayment.