Wanting a new house, but it will be a new construct

Ok bit of reference to what title states. We have a mortgage currently in Texas on our home but it’s a modular home on 1-acre. Now, we found another modular we would prefer and would fit our growing family better however, we at first had someone willing to buy our current house and the lender or owner of the modular home would use the house as a “trade-in” since it’s the same place we purchased our current house. But that buyer fell through. Now they’re saying unless we get a realtor involved we can’t proceed with getting new house and the process started on building and securing the piece of land we found. Now the issue we are running into is….. we don’t want to have to pay two mortgages, granted the new construction we might get 30-60 days before first payment, but we don’t have anywhere else to live to get this one ready for sale, walk-through etc. and we can’t afford 2 mortgages. And pretty sure our debt to income ratio wouldn’t allow us to do the “bridge” loan or home equity/cash out. So ideas?