I've heard about programs like Relaunch and Real Success, but I'm not sure if they're worth it.

If you purchased it for $100k and selling for $120k - it's not worth exchanging.

Typical requirements for a HML: recent bank statements, credit report, appraisal/BPO with as-is and ARV, sales contract, scope of work/budget-draw schedule, track record/previous purchase and sales HUDs/ALTAs showing the construction holdback amount, etc.

I don’t know if it would be worth it to do a 1031 after only a year unless you’re buying both properties for much less than their worth assuming 10% in selling costs (which might offfset any tax savings over just selling the contract) if the property goes from $100k to $110k by next year your taxable gain will already be zero after selling costs.if you plan to sell soon anyway  I think I’d lean towards just selling the contract and freeing up the money, saving loan and interest costs.

One of the siblings then buys out the others' interest in the land trust - but nothing of substance is recorded at the county.

How much will it be worth after it is complete ? 

Pay her consideration and record a Memorandum in the county of the property.  

I'll go first: I don't have an exact count but my PM tells me it's 20+ in a 1,000 sq foot townhome.

CFRI (cfri.net) has a general meeting this Tuesday evening…Would be worth the visit.

Also worth noting that rate isn't as important as people make it out to be.