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.
-- Tom