soop. I have a dear friend in your position. Her husband, a civil engineer, has drawn up plans to build a high tech retirement home on the south coast, and they will pay for it by releasing cash from the sale of their family home. She is in relatively poor health and at 65 is still working part time until they sell their house. They will rent somewhere nearby, live off their pensions, and hope they don't overspend so their new house is built quickly and efficiently. It's a big gamble, and a leap of faith in her husband staying fit enough to complete the project - he is nearly 70. The timescale is 3 years from selling the house to finding a plot, getting planning permission, renting a house, building the new house and being able to move in. She's quite anxious about it, but it's been his big dream to build his own house. If they wait any longer, it won't happen, but there are obvious risks, health-wise.
They've weighed up the pros and cons and, on balance, the adventure outweighs the risks, so she's put her trust in him being able to do it. However, he understands she won't be able to muck in.