There are many cost effective ways to connect a generator that are safe
although they may still be a technical violation of the electric code
that is enforced in your area.
In some recreational vehicles the cord that is used to connect the
vehicles electrical panel to the park outlet at the site is plugged into
an outlet from the generator when running on the onboard power. Since
the cords male cap is dead when unplugged from either outlet and it
cannot be plugged into two receptacles at once there is no danger of
electric shock from contact with exposed energized plug blades and no
likelihood of a back feed or interconnection of the two power sources.
Mobile homes are sometimes equipped with a fifty ampere cord and plug
assembly to connect them to power. Mobile home park service pedestals
are often equipped with a NEMA 14-50R pattern receptacle for just that
reason. It is true that the code does not sanction connecting a sub
panel to it's supply feeder via a four wire ranch receptacle and a range
cord set but like a mobile home were the same code permits the practice
it can be done safely. The total cost of the additional parts is less
than forty dollars US. When the need for emergency power arises you
unplug the cord from the outlet and plug it into an appropriate
recreational vehicle extension cord from the generator.
For one hundred dollars worth of parts you can set up a small sub panel
with two mechanically interlocked breakers to control the power to it.
There is a kit available for most SquareD panels that will interlock the
main breaker and a breaker in positions 2/4. The breaker in 2/4 serves
as the generator disconnect and the interlock keeps it from being closed
at the same time as the main breaker. Total cost of parts is less than
$120 US including the cost of the inlet box into which the generator
cord gets plugged.
All of these have some things in common. You would have to modify any
of them in order to create a back feed hazard. They can be connected by
any healthy adult without special knowledge or skill. They cost less
that an equivalent ampacity transfer switch.