I may have some hard money lenders but might be easier to make something happen if there are multiple being sold.

You could also consider a reverse 1031 exchange, where you buy the new property first.Make sure to identify multiple properties (up to three) to keep your options open, and try to negotiate longer contingencies with sellers.

I would rather not go to multiple lenders trying to figure out who does what if someone on here has had good experience with a particular lender already that does this type of loans.

I invested in Jacksonville, FL, because my old job would fly me there multiple times yearly.

We vetted a  handful of "turnkey" companies and REI Nation was the best in terms of reviews across multiple sources. 

It's much easier to set things up right than to have to transition them later when you have multiple properties and many, many transactions.

Remember, I sent a signed and amended the agreement on November 28th, sent it to them for signature, received confirmation of their receipt, wired funds, requested multiple times they send me the fully executed agreement, never received a fully executed copy back from them and finally was questioned by them yesterday as to why I altered the agreement (meaning there was no meeting of the minds since it's therefore proven that they didn't even look at it).I have rescinded my offer to enter into a contract with Estate Legal for lead generation services and am now seeking a full refund, including my cost of wiring the funds. 

If i sell my SFR rental for $450k and equity is, for example, $200k...Can i invest 100k into a new SFR worth $275k and invest the remaining 100k into a sponsored DST or TIC (which deals are usually multiple hundreds of thousands of dollars?

If you have just one business it's not too bad(My wife uses it for hers) but it starts to get really expensive if you have a lot of doors and or multiple businesses. 

I am a long-term investor with a buy and hold property in Brooklyn, NY and I also own multiple lands in Florida and Mississippi.